Chapter 1: The Scientific Method
Who are you?
Tell us a little bit about yourself. (Name, Rank, Serial Number, Why are you taking this class, etc.).
As a geographer - Describe to what extent you believe your approach to the discipline is scientific and to what
extent is your approach is not scientific? Also, do you consider yourself to be a scientist or not and why?
Instructor Post:
Thanks for the intro. It really does help to have a little bit of an idea about you as I teach this class.
However, since I don't have faces tied to these little bios my memory will scramble you folks up a bit.
Cathy will become a weather forecaster from LA and Pete will be a process engineer in the semiconductor industry. Anyway - A little bit about me:
I meant to ask you to tell me a little bit about yourselves in this first thread. That part of my post must
have been lost in the vortex… anyway here is a little bit about me
I got a B.S. in chemistry from Union College in upstate NY. I'm a southern cal boy who grew up starting
in Laurel Canyon (hollywood hills) and later in Santa Barbara. I taught high school for a while in SB but
the vow of poverty was too much and I opted for the fat paychecks in the semi-conductor industry at
Santa Barbara Research Center, then Hughes Aircraft then Raytheon. Big paychecks but only two
weeks of vacation a year and working in rooms with no windows, generating toxic waste to make
weapons. Working as a process engineer in the aerospace industry was not really what I wanted to be
when I grew up. Had a spiritual/career awakening and went to grad school at UCSB in Geography. First
job here at DU. Love being a geographer. Love the cool questions I can explore with GIS and Remote
Sensing. I consider myself a scientist yet maintain that the most important questions in life are outside
of the domain of science. Sadly, I think humanity as a whole answers both science questions and nonscience questions rather poorly. That is why the world is overpopulated, polluted, and violent. I hope to
make my small contributions to the improvement of the human condition by using science to
demonstrate that the world is polluted, overpopulated, and consequently violent. Wish me luck. I think
it is very interesting how many strange similarities there are between me and each of you in some
respect. Chemistry degrees, working as an engineer in industry, etc. I hope this class serves your
needs.
Cheers,
Paul
Natural Science, Social Science, and the Humanities
Classify the following questions as to being in the domain of Natural Science, Social Science, or the Humanities
(combination answers are ok). Also characterize these questions as normative or objective.
1) What is the best form of government for human society?
2) Does smoking reduce life expectancy?
3) What is love?
4) Does God exist?
5) How much CO2 can the world's oceans absorb?
6) What is the human carrying capacity of the planet earth?
7) What elements and minerals exist at the very center of earth?
8) How do real estate prices vary as a function of distance from the downtown?
9) How can pine beetle damage be prevented in Colorado?
10) How has the adoption of catalytic converters changed the spatial and temporal variability of atmospheric carbon
monoxide concentration in Los Angeles?
Instructor Post:
The answers to these questions are not always hard and fast.
Most of you came up with pretty much the same answers which seemed
reasonable to me. I found it interesting that very few of you answered the
carrying capacity of the earth question as Natural Science / Objective.
I think it is a Natural Science / Objective question. Clearly there can be some
Debates about some of these.
Are we all brains in jars?
Suppose someone claimed that the true nature of reality is that our experience of being conscious, mobile
human bodies on the surface of the earth is WRONG and that really we are merely brains in jars on a giant
shelf somewhere (perhaps in a manner similar to the movie The Matrix). And,. our sense that we actually
control our physical bodies is only an illusion. Comment on the 'Scientific' nature of such a proposition. Is this
kind of hypothesis a scientific one? Why or Why not? (every student in the class should post a one paragraph
response to each thread of each discussion board).
Instructor Post: I liked your postings on our first discussion board. One comment I wanted to
make is about the 'Could we all be brains in jars' question as a scientific proposition. I will riff on
this a tad. Basically I would argue that this is not a very scientific proposition because it fails the
'Realist Philosophy' metaphysical belief of most scientists. Most of us believe that we are sentient
biped animals on the surface of a planet we call earth. Of course - it is not completely impossible
that we are 'brains in jars' or some other 'Matrix-like' entities. However, the burden of proof is on
those who make such a wild claim and noone has really succeeded in doing so. Most of us still
believe we are pretty smart apes on planet earth. We have to go with that until convinced
otherwise. This is really the point that Garrett Hardin was making in his paramount principles
paper. Make some important claims and challenge the rest of the world to prove you wrong. Thou
shall not exceed the carrying capacity ideas. Physics has succeeded in this. The 2nd law of
thermodynamics is pretty much accepted as true. Nobody has proven it wrong by developing a
perpetual motion machine or some other means of 'falsifying' the 2nd law. This is how 'theories'
work. Note also that stating that there is an unknowable God who designed the universe is just as
unscientific as stating that we are all brains in jars. There may be a God but those ideas and
arguments are outside the domain of ‘science’ as it is typically practiced.
Chapter 2: Fundamental Research Concepts Research Methods Discussion board
What is a paradox anyway?
Define the word 'Paradox' and provide an example. Also, explore the various combinations of the ideas of
discrete and continuous space and time as they pertain to Zeno's four paradoxes. Are any of them TRUE
paradoxes? Explain.
Correlation is not causality
A social scientist finds that there is a correlation between the percentage of students at a given elementary
school recieving the 'Free Lunch Program' and the percentage of students that 'Do not meet standards' on the
CSAP (Colorado Student Assessment Program) standardized test. The Governor sees these results and
concludes he has a 'Win-Win' opportunity here: CUT the Free Lunch program. This will 1) Lower Taxes AND 2)
Lower the fraction of children who fail the CSAP test. Comment on this little vignette in the context of the
statement: "Correlation is not Causality".
Instructor Post: The social scientist has done nothing wrong. Noting the correlation is interesting and
potentially informative to policy etc. The conclusion of the governor is erroneous. The free lunch
progam is most likely a proxy measure of other 'confounding variables' that are difficult to measure.
These 'confounding variables' (poverty, single parent homes, time spent with children reading, etc.)
may be more directly 'causal'. It is very unlikely that the free lunch program is causal in this situation.
Is Evolution Falsifiable?
Most of you are probably familiar with the on-going and perhaps eternal debates about Evolution, Creationism,
Intelligent Design, and the Flying Spaghetti Monster (http://www.venganza.org/). It is an interesting debate with
some interesting twists. The scientific method IS the scientific method BECAUSE it allows itself to EVOLVE. So
there are some strange self-referential kinds of curves here. Creationism is basically a NON-EVOLVING
statement of truth by fiat. Nonetheless - the THEORY of EVOLUTION (as posited by Charles Darwin back in
his 1859 classic: The Origin of Species) is an interesting one to consider from a scientific perspective. In
traditional 'philosophy of science' parlance a 'THEORY' should be Falsifiable. It is an interesting question to ask
whether or not Evolution (the set of ideas that there is natural variation, some varieties are more suited to
survive than others, these varieties tend to reproduce, etc.) is a falsifiable theory. Comment on whether or not
you think the theory of evolution is falsifiable - If you think it is provide examples of what would constitute a
'disproof' of the theory of evolution. Also, comment on this question as it pertains to the ongoing debate about
evolution and creationism.
Instructor Post:
Janine’s Answer was good: Homo Sapiens skeleton next to stegosaurus bones would be
problematic. I’ve heard evolutionary biologists say: “housecats in the Pleistocene” and other
such empirical observations would be very problematic for the theory of evolution.
Evolution is a funny one:
Interesting Article in the Scientist
http://www.the-scientist.com/newsletter/etoc/20100101.html
Chatpers 3 & 4 Research Methods Discussion Board
Geodesy – What is it anyway?
What is Geodesy, and what are some basic geodetic properties that are measured? How important are
geodetic measurements to your particular inquiry? Explain.
Instructor Post: Geodesy is some of the technical substrate of Geography. Your answers are all pretty
right on. there are interesting military and historical stories about geodesy. A cool book that is an easy
read is Taylor MOrrison's: The Coast Mappers - a story about the early days of the National Oceanic
and Atmospheric Administration (NOAA). A lot of geodesists were hired by Ohio State University in the
post world war two era - paving the foundation of a very positivist and technical department for many
years.
What about YOUR research question?
Prepare a short draft of one of your research questions and explain what methods (qualitative or quantitative)
and data (primary or secondary) you anticipate you will use to answer your question.
Various Instructor Posts
Parrying Post-Modernists and Postivists Oh My!
What role have ideas about quantitative and qualitative methods played in the 20th century history of
geography as an academic discipline? How do geographers who prefer to call themselves scientists tend to
feel about ideas of 'meaning' and 'experience' as they pertain to their approach to geographic inquiry?
Instructor Post: I asked this question primarily to make you aware of the broader nature of geography
in general. As GIS people we tend to land more in the positivist / scientist domain. Geography
departments across the U.S. have different flavors across this spectrum. departments that lean in the
positivist direction include places like UCSB, ASU, Univ of Maryland, DU. Post Modernist / Social
theory oriented departments would include U of AZ, Kentucky, Minnesota. Different flavors. For more
information on this see the Schaeffer - Hartshorne debates.
Chapters 5 & 6 Research Methods Discussion Board
Is census data primary or secondary and is it an explicit report?
Describe the spatial hierarchy of census data. Explain how census data is or is not based on explicit reports
and how this related to issues of privacy and confidentiality. Extra Credit: What kind of privacy violations was
the census bureau accused of committing in the late 1930's and early 1940's? Were they justified?
Instructor Post (provided by former student Michelle Guzdek):
Census data is a secondary source explicit report data, because it is not collected for a specific
research project. To protect privacy, the actual completed forms are not made available for 72 years
and the data is aggregated to spatial units designed to keep individual responses private.
Below is an example of the spatial hierarchy for major census units:
E n t i r e
U n i t e d
S t a t e s
C e n s u s
R e g i o n s
C e n s u s
D i v i s i o n s
( f o u r )
( n i n e )
States (50 plus U.S. Territories)
C
o
u
n
C o unt y
t
i
e
s
s ub di vi si o ns
C e n s u s
C e n s u s
P l a c e s
T r a c t s
Census Block Groups
Census Blocks
The U.S. Census was accused of being involved with the Japanese internment program by highlighting
areas of Japanese concentration as small as city blocks at the onset of the U.S.’s involvement in WWII.
It is also recorded that before the Japanese attack on Pearl Harbor, FDR ordered the Census Bureau to
collect information on “American-born and foreign-born Japanese”. As to whether they were justified
in doing so... If I was in charge after such an attack I may have bent the rules a little also. I would not
have used internment camps, but I may collect data and monitor persons of interest. We still do it
today! – Opinions on this issue vary dramatically
What is intelligence anyway?
Suppose you are assigned the task of measuring the intelligence of the incoming freshman students at the
University of Denver. Explain how you might use existing data (e.g. High School GPA, SAT scores, ACT
scores, etc.) OR develop your own test to measure intelligence. Define the 'construct' we call intelligence.
Explain how you might plan to measure and code your measuremtns and discuss the reliability and validity of
these measures. Finally comment on an experimental design that addresses gender and spatial cognition. Do
guys never ask for directions because they have better spatial cognition abilities? How might you design an
experiment to answer that question and why might it be a controversial study?
Instructor Post (pretty good answer provided by former student Justin Stein): In the interest of saving
money and time it would be essential to use the available data such as High School GPA, SAT or ACT
scores and Class Rank.
Intelligence is the measure of cognitive abilities using various tests of reasoning, problem solving,
analysis, language and learning. In other words, it encompasses probably too much to effectively
measure.
My test would use available data of past performance to assess the overall intellectual quality of the
incoming class. In the case of GPA I would attempt to normalize the GPA of students from different
schools by establishing a class rank and a mean for each source high school to reduce the effects of
grade inflation. In addition to this, it would probably be necessary to also assess each high school's
overall quality so as to not punish (or at least misrepresent) those students who worked hard in a
difficult program. This would have to be incorporated in the GPA data. The SAT and ACT scores
would be easier as they are already designed to be ranked and assessed (hooray for them completing
the hard part!) and this data at least can be somewhat reasonably applied as a measure for the
students. Using these variables we can then decide on a weight and determine the 'score' each
student and establish a curve to represent the students. Of course, an experiment to measure such a
nebulous idea is going to be filled with bias (in testing, gpa, high school assessment and weighting)
from nearly all aspects of the study. If you wanted to get serious, you could start normalizing the data
in other ways to make up for this bias and testing the predictive abilities of your data but that is going
to require quite a grant!
In the design of gender and spatial cognition, there have been some prior studies on the way in which
individuals of different genders organize directions and space. In the experiment it would be best to
incorporate multiple ways of assessing space (ie distance, landmarks, and other forms of mental
mapping) and weight the techniques to create an equal measure of spatial cognition across gender
boundaries. Easier said than done and ultimately there will be controversy regarding the selection of
'ways' that men and women perceive space, the weighting of spatial measurement and other factors. In
the ideal experiment, we would have a system where women and men will rate equally in their spatial
cognition and then we can begin to sample spatial cognition of other variables of interest. Another
grant will be required.
Public Opinion of the Abortion Issue
Describe how you would go about assessing and surveying public opinion of the controversial issue of abortion
in the United States. Be sure to include a description of issues such as:
wording effects (Should a woman be allowed to murder her unborn child? vs. Should a woman or the
government have control of that woman's body?)
Context effects
Counterbalancing of questions and likert scales
non-response bias
face to face vs. web based vs. paper
No Instructor Post for this question available
Chapter 7 Research Methods Discussion Board
Research designs in general and for you….
What are several specific research designs, and what are some of their strengths and weaknesses? How might
your particular research project fit into any of the designs described in the text?
Instructor Post (drawn from postings of former students)
Student I: The following is a description of some specific research designs.
The first two examples are nonexperimental designs. The first is one-group with a single measurement.
This is the simplest possible design and involves taking one measurement of a group. This data is only
good to measure the absolute level of some variable in a population. A better nonexperimental design is taking
multiple pre- and post-test measurements of one-group. This allows one to better judge whether an
event caused a change in the population or it was an on-going trend.
The next two examples are experimental designs. The first is the simplest design and exposes one
group to a condition, takes a measurement, exposes the group to a different condition and take another
measurement. An improvement on this design is to perform that same manipulations to two groups,
but subjected the second group to Manipulation2, to observe possible effects of the order of
manipulations.
My research would involve statistical empirical control and would be a nonexperimental study with one
group of data looking at posttest observations. My research will be focusing on the risk of a pathogen
affecting healthy trees. To determine the risk, I will be looking at trees that are already affected with the
pathogen (E – event) and then taking measurements (M) about that event. It is impossible for me as a
geographic researcher to manipulate variables is this research field. Some of the variables that I will be
looking at are canopy cover, precipitation, watershed, proximity to trails, and distance between trees,
all of which cannot be manipulated.
Student II: Research Designs fit into one of to very broad categories: Experimental and NonExperimental Studies. In experimental studies, at least on variable is created whereas variable are only
measured in non-experimental studies. Non-Experimental studies may involve physical and/or
statistical control, but they do not involve manipulated variables. Experimental studies refer
specifically to studies that involve the manipulation of one or more variable, or in other words involve
assignment control. Both classes of research design have their strengths and weaknesses. Generally,
within case designs are more efficient, as fewer cases are necessary to get the same amount of data;
lead to higher precision of estimation and power of hypothesis testing, even given the same amount of
data; and reduce confounds because comparison groups are more nearly equated. Within case
designs also have some severe limitations including they always employ multiple measurements of the
same cases and in experimental designs, multiple exposures to different conditions of the independent
variable, run the risk of changing cases somehow as the study goes on, producing order effects, and
they often simply can't be done, with many variables fundamentally reflecting inherent properties of
different cases that can hardly if at all be made to exist within the same case over time ( the ultimate
limitation). Since I will be working on building a web application for my capstone project my project
doesn't fall in line with the "traditional" research design types discussed in the text. Although my work
as a GIS analyst involves extensive use of models such as HAZUS-MH, ALOHA, HEC-RAS, and the like
to model the potential effects of natural hazards within the state of Washington. Of all the types of
research discussed in chapter 7 of the text, computational modeling is the one I am most interested in
and have the most experience with.
Build a computational model
Build/Describe a simple computational model that predicts the nubmer of daily telephone calls between any two
cities of the United States with a population greater than 50,000. What data would this model need? How do
you think the number of phone calls would differ from the number of airline passengers between these cities?
Explain.
Needs and Instructor Post
The Governor’s Blue Ribbon Panel on Teaching Effectiveness
Suppose a Governor's Blue Ribbon Panel is tasked with measuring "Teaching Effectiveness" which will be
used to provide merit based funding to all the public K-12 schools in Colorado. They use the 'residuals' or
errors (See image below) from a regression of CSAP scores vs. % of students on the free lunch program to
measure this. What is the key 'Construct ' of this approach? How is it measured? Comment on the validity of
this approach.
Needs and Instructor Post
Chapter 8 Sampling Research Methods Discussion Board
Spatial Sampling: Validation of a Global Land Cover Data Product
Suppose you have been contracted by the United States Geological Survey to validate a global land cover data
product they have produced from satellite imagery and ground truthing. This map is essentially an image or grid
with millions of 'pixels'. Each pixel in this image is assigned a landcover category (e.g. ocean, lake, boreal
forest, desert, wetland, deciduous forest, grassland, wetland, etc). Obviously there are WAY TOO MANY pixels
for you to validate the accuracy of every one. To validate just one pixel you would have to travel to that pixel
with a land cover classification expert who would tell you what the real world 'actual' value of that pixel was and
then you would compare that assessment to what the USGS data product said it was. Now, here's the hard
part: Design a sampling strategy to perform this validation. Will you use a probability or non-probability design?
Why? How will you generate a truly spatially random sample of points on the earth's surface? (i.e. how would
you generate the X, Y coordinates of Latitude and Longitude). Would you want a simple random sample of the
surface of the earth (keep in mind that roughly 75% of your points will be in the ocean if you do), or might a
stratified sample make more sense? If small area land covers such as wetlands are particularly important does
this suggest that stratifing your validation sample is appropriate? Explain.
This is a hard question with many issues: 1) Spatial Resolution – What is the spatial resolution of the
data product and how is one expected to deal with ‘Mixed Pixels’. 2) Spatially Random on a Sphere –
several of you mentioned getting a computer to ‘randomly sample’. Too pat an answer. To truly
randomly sample the earth (with any given square pixel having an equal chance of being sampled as
any other given square pixel the probability of the latitude coordinate (Y) has to change as a cosine
function (i.e. using uniform random to generate longitude (X) and latitude (Y) coordinates will
OVERSAMPLE toward the poles). 3) Undersampling land covers of low areal extent (e.g. Wetlands and
riparian areas) I would go with stratified sampling to make sure I got enough assessments of small
areal extent areas like wetlands. 4) Real World Considerations: Bryan and Megan had good ‘Real World’
comments with respect to cost. I was surprised no one mentioned simply using the high resolution
imagery in Google Earth to do some ground truthing. What do folks think of that? Another cool thing
to be aware of is the “Degree Confluence Project” (http://confluence.org/ ) Definitely not a random
sample but a cool project that is attempting to provide ‘ground truth’ photos for every intersection of
integer latitude and longitude. Check out the web site.
Paul’s Assessment of the Writing Program here at DU
In the past few years DU has instituted a writing program for first year undergraduate students. I teach a piece
of the program as a first year seminar instructor. The first year seminar course is taught in the fall and is
followed in winter and spring by writing courses that are taught by lecturers in the writing program. I have
wondered what students thought of the writing program sequence and have surveyed many of them. Whenever
I run into an undergraduate student (having dinner with them after a Marsico speaker, or on a field trip, or as
they pass by my office) I often query them as to what they think of the writing program. The response of these
students when asked what they think of these writing courses is uniformly negative (Those writing courses
SUCK! is a pretty accurate paraphrase of many of their statements). Anyway, critique this summary of my
study:
I assessed the effectiveness of DU's writing program by surveying students who have taken the writing
sequence. The students hate the courses so the writing program is not effective.
Is this a probability or non-probability sample? How 'representative' and how 'generalizable' are my conclusions
based on my survey of the students I sampled? How valid (or logical) is my conclusion that the writing program
is ineffective based on the responses to my survey?
Instructor Post (provided by former student Michelle Guzdek):This type of sampling is non-probability
sampling, specifically called convenience sampling. You asked students that you happened to run into
what they thought of the course. Beforehand you could not say what the probability was of a particular
case being part of the sample. Since you used non-probability sampling you cannot say with much
certainty how well the sample represents the sampling frame, so I would say it is not very
representative.I think you conclusions are not very generalizable. I don’t think that your conclusion is
very valid in determining how effective the writing class is. It could be that students just hate writing in
general and no matter how effective the class is they would have a negative opinion.
Great Answer from Megan Ross
This is a non-probability sample, specifically a "convenience" sample, because you are surveying
every student you happen to run into, and there's no reasonable way to estimate the likelihood of
knowing which students will be in the sample. There is also no way of knowing whether the sample
group is representative of the larger population, because the sampling design is nonprobabilistic. Still,
because these methods are common in social science surveys, the results could be generalized to the
undergraduate population. I would want to know more about the study, especially, how many students
were surveyed? (If only ten students were asked, I'd be wary; one or two opinions could sway the
whole field.)
The real reason I'd throw out this study isn't because of the methods, but because (based on the tone
of the summary) the students likely aren't responding to the construct variable (effectiveness), but to
their experience with the class (enjoyableness). When testing whether cough syrup works, you study
whether it suppresses coughing, not whether it tastes good. To really study the effectiveness of a
class, it would be best to employ a pretest/posttest method wherein you could establish a baseline and
evaluate change. Skills and comprehension would be important to assess; opinions likely would not.
Sampling as a Geographer
Think of a good geographic question that will require the sampling of cases from a population. Define your
population, your sampling frame, and your sample. Choose and defend a sampling method. Discuss any
problems or issues associated with your approach.
Needs and Instructor Post but Answers will vary dramatically
Chapter 9 Statistical Data Analysis Research Methods Discussion Board
The Modifiable Areal Unit Problem
One of geography's coolest and hardest problems is the Modifiable Areal Unit Problem (MAUP) that was
most eloquently and rigorously identified by Stan Openshaw. It manifests as a problem of both scale and
aggregation. One example that helps illuminate it is the idea that you could take a spatial dataset that had
demographic data of ethnicity fractions and some other variables like percent literate, income, education,
whatever. Now, by changing the way you aggregate this data and/or by changing the scale at which you
aggregate this data you can often get the statistical relationship between variables (e.g. % Black and %
Literate) to vary from R-squares of almost +0.9 to -0.9. The MAUP can often provide examples that support the
bogus argument that you can say anything you want with statistics.
("There are lies, damn lies, and statistics." Mark Twain (?)).
I try to make my test questions fun and instructive. Below is an image of a test question I put in my Intro to GIS
course (with answers). Look at this question and do some research on the MAUP (this is a case where
Wikipedia is woefully inadequate). Then, in your own words define and explain the Modifiable Areal Unit
Problem in language that your grandmother could understand.
See Kristina Yamamoto’s Comprehensive Exam Question Answer in Powerpoint
MAUP_yamamoto_dis_board_9_3.doc
The Free Lunch Program and CSAP scores revisited
Let's go back to the example of Colorado's high stakes K-12 testing: CSAP scores. Basically, the research into
the relationship between the % of students enrolled in the free lunch program and the school's average CSAP
score is a simple ordinary least squares regression approach.
Would you describe this as an experimental design or a design of analysis?
No experimental control so it is a design of analysis
What are the constructs in this research and how are they measured? Comment.
Teaching Effectiveness
What are the statistical parameters that are measured via this methodological approach?
Slope and intercept of linear relationship between percent free lunch and CSAP scores of schools
How would you predict the average CSAP score of a school based on the fraction of its students enrolled in the
free lunch program?
As percent of free lunch program goes up CSAP scores go down
To what extent does a study of this nature involve the four principle scientific conepts of: description, prediction,
explanation, and control?
Description and prediction yes. See posts for Explanation. Control no.
Tobler’s First Law of Geography and Spatial Autocorrelation
Waldo Tobler (who I am proud to say signed my dissertation and master's thesis) is credited with coming up
with one of Geography's few Laws:
"Everything is related to everything else, but near things are more related than far things."
This is in essence a terse summary of the idea of spatial autocorrelation. Define spatial autocorrelation and
explain how geo-statisticians take advantage of spatial autocorrelation to perform spatial interpolation tasks
using methods such as Inverse Distance Weighting, Kriging, etc. Name some typical datasets on which we
perfrom spatial interpolations to serve some purpose (an example would be the temperature map on the
weather section of the USA today).
Needs an Instructor Post
Handedness and Eyecolor – Is there a relationship?
Suppose you wanted to test to see if there is a relationship between 'handedness' (i.e. people that are lefthanded vs. people that are right-handed) and eyecolor (for simplicity's sake let's go with blue, brown, and other
as eye color classifications).
How would you go about testing this?
Is this a parametric or non-parametric statistical test?
What statistical test would you use?
Are the measurements of your constructs nominal, ordinal, interval, or ratio?
Suppose you did find a relationship between eyecolor and handedness - How would you explain what that
means to a layperson?
Needs an Instructor Post
Chapter 10 Data Display Research Methods Discussion Board
How cool is a map?
If you fancy yourself a cartographer, or if you find this chapter on data display even moderately interesting you
should entertain the idea of buying Edward Tuffte's classic book: The visual display of quantitative information.
http://www.edwardtufte.com/tufte/books_vdqi
One of the very cool visual displays of quantitative information described in Tuffte's book is Minard's map of
Napoleon's march on Russia (see image belown or go to this link:
http://strangemaps.files.wordpress.com/2007/12/minardmap.jpg ). Study this map and determine how many
variables this map communicates to the map reader. How well does this map communicate? If a picture is
worth a thousand words, how many words is a map worth? Consider how a GIS can display data, and modeled
results using spatial data? How can that be useful? Data display is a BIG deal and the best image processing
packages remain on our shoulders. Provide some general comments on the utility and power of data display
techniques including mapping.
Needs an Instructor Post
How cool is a scatterplot?
The image below contains the 'x' and 'y' coordinates of four bivariate datasets. Plug these numbers into excel
or some other program such a JMP (if you have it). Run a simple little ordinary least squares linear regression
on these numbers. Record the mean of x, the mean of y, and the slope, intercept, and r-squared parameters for
each regression. Now make a scatterplot of each of the four sets of numbers. Comment and explain on the
value of a scatterplot in the context of this exercise.
Instructor Post (provided by former student Cathy Walker):
How cool is a histogram?
In the image below I have pasted in an image that I 'snagged' from a statistical software package called JMP.
One of the first things you should do with data is "look" at it. This includes graphing univariate distributions
(histograms), plotting bi-variate distributions (scatterplots), and mapping. The image below includes the first few
numbers in a table of 400 numbers and a histogram that was derived using all 400 numbers. What can you see
in a histogram and why are they so useful? The image also includes a boxplot. Google 'Box Plot' and explain
how one is drawn. Where have you seen histograms in everyday life? What is the use of graphical devices
such as histograms and boxplots?
Everyone in the class should post a histogram of the distribution of household income in the united states. Find
the best data you can on the web and make a histogram of United States Household income. Next week I want
comments on the variability of the postings to this question. (Post graphics of these histograms)
Instructor Post (provided by former student Cathy Walker):
The frequency counts of values in a distribution can be shown with a histogram.
In a histogram, the frequency values is shown as a series of veritcal barsk one for
each class of values. Data are discrete, the height of each bar representing the
frequency of values in a particular category or integer value. A box plot or
boxplot (also known as a box-and-whisker diagram or plot) is a convenient way of
graphically depicting groups of numerical data through their five-number
summaries: the smallest observation (sample minimum), lower quartile (Q1),
median (Q2), upper quartile (Q3), and largest observation (sample maximum). A
boxplot may also indicate which observations, if any, might be considered
outliers. Boxplots display differences between populations without making any
assumptions of the underlying statistical distribution: they are non-parametric.
The spacings between the different parts of the box help indicate the degree of
dispersion (spread) and skewness in the data, and identify outliers. We see
histograms more so than box plots in our everyday lives. Box plots are used in
the news to recently display the changes in housing prices, employment, year to
year retail sales, and other such econmic measures on eveyone’s mind these
days. Boxplots allow us to graphically see the mean,minimum, maximum, and
other important stastical measures that are not easily determined for just looking
at a list of numbers in a table or spreadsheet. Histograms allow us to see
frequency distributions of present in our data, that without a histogram couldn’t
be determined visually by just looking at the numbers contained in a data table.
Chapter 11 Reliability and Validity Research Methods Discussion Boards
Comments on last weeks histograms of household income in the United States
Look at all the histograms posted last week. Which one do you think is the best representation of the
distribution of income in the United States? Why are everyone’s postings so different? What is the
‘Truth’ regarding the distribution of household income in the United States?
Tests and reliability
Consider some 'test' or measurement that has been made of you in your life (e.g. SAT test, driver's test,
urinalysis, whatever). Describe how you could assess the reliability of that test and how it can be difficult to test
the reliability of a measure over time for a given individual. Also discuss any issues of the validity of this test or
measurement with respect to its purpose (e.g. are driver's tests a VALID means of assessing whether or not
someone should be issued a driver's license, are SAT tests a VALID assessment of 'scholastic aptitude'?).
Also, provide a generic definition of 'reliability' with respect to the issues discussed in this chapter.
Needs an Instructor Post
Public Opinion Surveys and External Validity
My master's thesis involved sending out 3,000 paper surveys to a randomly selected set of the registered
voters of Santa Barbara county california. About 750 surveys were sent back to me filled out. The survey
involved questions about population growth, immigration, and the social, economic, and environmental impacts
of population growth. The state of California was about to have a state-wide vote on a citizen led initiative (Prop
187) that was very 'anti-immigration' in its spirit (it pushed for stronger enforcement of immigration law, denial of
many benefits such as vaccinations and education to illegal aliens etc.). Suppose that I concluded that Prop
187 was going to pass based on the responses to the immigration related questions in my survey. What are
two or three significant threats to the external validity of my conclusion? (It turns out I was correct in predicting
that Prop 187 would pass but that is neither here nor there).
Instructor Post (provided by former student Cathy Walker):
There are three significant threats I see to the external validity of your conclusion concerning Prop 187. First, the
number of surveys you received back in ratio to the number sent, you only received back only 25% of the total surveys
sent out. Secondly, you chose a small geographic area close to the southern US-Mexico border. Fixating on such a
small area could insert bias into the results depending on whether Santa Barbara residents tend to be pro or antiimmigration rights, such a small geographic areas of California is hard to use as a representative of the whole state,
especially one the size and population of California. And lastly, as with all surveys concerning elections or polls, people
can change their mind from what they initially responded with in your survey resulting in a drastically different
outcome when they go to the real polls to cast their vote.
CSAP scores and the % Free Lunch Program Re-Re-visited
Comment on the internal validity of the claim of a researcher who says that if he had experimental control he
could raise the average CSAP scores of a school if he had the ability to significantly lower the percentage of its
students who received the free lunch program (not by changing the students but by simply denying them the
free lunch). Do you think this idea has any internal validity? Why? How could you test the internal validity of
this idea?
Instructor Post – Experimental Control (see answer provided by former student Cathy Walker)
Internal validity is centered around finding the truth in research conclusions about the causal
relationships observed in a study. In this case the CSAP scores and % of students that get free
lunch seem to have some type of correlation but the causal relationship between these two
entities cannot be established. There is no internal validity to this correlation as so many
other factors can be contributed to a student’s performance on the CSAP test such as low
income, lack of family support, lack of parental education, etc.. One way to test the internal
validity of the correlation between free lunch program recipients and CSAP scores would be
to cease the free lunch program and supplement this program with increased public
assistance (for food) for those children receiving free lunch for a given time, and test the
student population to see if CSAP scores have changed. My guess would be that the results of
the test would still reveal lower scores in schools that have a higher % of low income students
and a higher score in schools that have a lower % of low income students, thus revealing that
other causes may be contributing to the difference in CSAP scores throughout the state.