correlation coefficient

Psychological Research Methods
Excavating Human Behaviors
Stolen from Made my Mr. Kaplan, majorly altered by Mr. C
Altered for GV by Mrs. O’Mara
 Research Methods Questions
What is a theory? A hypothesis?
 What are 3 measurements of central tendency?
 What is standard deviation?
 What are types of descriptive research?
 What is correlational research?
 What is a correlation coefficient?
 What is experimental research?
 What is an operational definition?
 What are confounding (extraneous) variables?
 What is validity? Reliability?
 What is the placebo effect?
 What is independent variable? Dependent variable?
 What is a double-blind study?
 What is bias? Hindsight bias? Experimenter bias?
 What is random sampling?
 What is a correlation coefficient?
 Experimental group? Control group?
 What is a case study?
 What is a longitudinal study? Cross-sectional study?
 What is an Institutional Review Board?
 What are the APA’s ethical guidelines for animal research?
 What are the APA’s ethical guidelines for human research?
Why do we need science?
Science is usually the best thing we have. Without
science, we’d still be drilling holes in people’s heads
to get the demons out. We’d hold on to our beliefs
even if they were wrong.
What is Experimental Research?
 Explores cause and effect relationships.
 Has control and experimental groups
 Laboratory experiments are good at controlling variables.
Eating too many bananas causes
Experimental Vocabulary
 Independent Variable: factor that is manipulated (the
medicine) (What you are doing to the subject)
Dependent Variable: factor that is measured (anxiety)
Extraneous or Confounding Variables: factors that
affect DV, that are not IV. (factors that screw up the
experiment!) (other meds?, other sources of stress)
Experimental Group: Group exposed to IV (those who
get the pill)
Control Group: Group not exposed to IV (Those who get
the sugar pill)
Placebo: inert substance that is in place of IV in Control
Group (The sugar pill)
Steps in Designing an Experiment
Pick Population: Random Selection then Random
Operationalize the Variables
Identify Independent and Dependent Variables.
Look for Extraneous Variables
Type of Experiment: Blind, Double Blind etc..
Gather Data
Analyze Results
Let’s do an experiment.
 Hypothesis: The red pill will reduce anxiety.
 We operationalize the definition of anxiety to mean those
whose doctors claim they suffer from anxiety.
 We find 100 people who fit the operationalized definition
 We randomly assign half the men to the experimental group
and half the men to the control group. (Same with women).
 I, the researcher, do not know which group will receive the
medication and which will receive the placebo. That means
this is a double-blind experiment. This will reduce
experimenter bias.
 The experimental group will receive the actual
medication. The medication is called the independent
 The control group will receive a sugar pill (the placebo).
 The research team will ask all participants to measure
their level of anxiety on a scale from 1 to 10. Anxiety is
the dependent variable (what is measured).
 The control group will usually report a decrease in anxiety
even though they received no medicine. This is called the
placebo effect.
 Now that the experiment phase is done, you must consider
the confounding variables. This is the stuff that will screw up
your experiment. Ex: what if the control group had a mean
age much less than the experimental group? What if the 2
groups had a different percentage of women?
 Our original hypothesis was: the red pill will reduce anxiety
by 40%.
 Results: The experimental group reported a mean of 10%
reduction in anxiety versus a 5% reduction for the control
 Theory: After several replications, the medicine has no
significant effect on anxiety.
Reliability and validity?
 A finding is reliable if it can be replicated. If subsequent
studies show that the red pill reduces anxiety then the
findings are reliable, thus supporting the hypothesis.
 A study is valid if it measures what it is supposed to measure.
If our experiment measured hypertension instead of anxiety,
then the test in invalid, even if it is reliable.
Is the TAKS valid and reliable?
 If a similar TAKS test given to a group of 8th graders produces
the same scores, then it’s reliable.
 If students fail the 8th grade math TAKS because the wording
is on the 10th grade level, then people might question the
validity. A valid math test tests math, not reading level.
Non-experimental types of research.
What is going on in this picture?
We cannot say exactly, but we
can describe what we see.
Thus we have…..
Descriptive Research
 Any research that observes and records.
 Does not talk about relationships, it just describes.
Types of Descriptive Research
 The Case Study
 The Survey
 Naturalistic Observation
 Cross-sectional study
The Case Study
 Where one person (or situation) is observed in
What are the strengths and weaknesses of using
a tragedy like the Columbine School Shootings as
a case study?
Longitudinal studies
 A subject is studied for a long long long time.
 Twins separated at birth are surveyed at ages 5, 10, 15, 20,
30 years.
Cross-sectional study
 Different groups of people are compared and contrasted.
 Blacks vs whites on attitudes towards psychotherapy
 Poor vs. middle-class on extrovertedness
The Survey Method
 Used in both descriptional and correlational
 Use Interview, mail, phone, internet etc…
 The Good- cheap, anonymous, diverse population,
and easy to get random sampling (a sampling
that represents your population you want to
Random Sampling
Why do we sample?
 One reason is the False Consensus Effect: the
tendency to overestimate the extent to which
others share our beliefs and behaviors.
Survey Method: The Bad
 Low Response Rate
 People Lie or just
 Wording Effects
 Social desirability
How accurate would a survey be
about the frequency of
diarrhea? Homosexuality?
Naturalistic Observation
 Observing and
recording behavior in
natural environment.
 No control- just an
What are the benefits and detriments of
Naturalistic Observation?
Correlational Research
 Detects how well one variable predicts, not causes
another variable.
 Does NOT say that one variable causes another.
There is a positive
correlation between
ice cream and murder
rates. Does that mean
that ice cream causes
 Studies show that there is a strong correlation between how
many books are present in a child’s home and college
completion rate.
 Do the books cause a person to complete college?
Correlation and Causation
 Three possible cause-effect relations
Distressing events or
biological predisposition
Measured using a correlation
 A statistical measure of the extent to which
two factors relate to one another
What is a Correlation Coefficient
Which correlation coefficient has the
strongest relationship? The weakest?
 A. .79
 B. -.88
 C. .09
 D. 3.6
 E. -.05
B has the strongest. E has the weakest D. is invalid
Analyze Results
 Use measures of central tendency (mean,
median and mode).
 Use measures of variation (range and standard
What is bias?
 Attitudes and beliefs that can skew results.
Hindsight Bias
 The tendency
to believe,
after learning
the outcome,
that you knew
it all along.
Many believe that Obama was better
for the country. Would we feel
different if McCain won?
Experimenter bias
 The people running the experiment think they know the
truth already.
 Ex: The tobacco industry funds an experiment. The
results: cigarette smoke has a neutral effect on asthma.
 Ex: A doctor wants to cure AIDS, so she unconsciously
biases the experiment by giving the sickest patients the
2 types of statistics
 Descriptive statistics are used to reveal patterns through the
analysis of numeric data (describe what is there) (Ex: 25% of
Republicans pray before sex.)
 Inferential statistics make an inference about the population
from a sample. Ex: predicting how people will vote based on
polling a 1000 people.
What is an institutional review board?
 All academic research must be approved by an institutional
review board at a local university. They review it for ethics and
procedural errors.
Ethical guidelines for animal research?
 1. must have clear scientific purpose
 2. humane care for animals
 3. animals must be trapped or bought legally
 4. suffering must be minimized.
Guidelines for human research?
 Coercion – Participation must be voluntary
 Informed consent – They must know that they are
involved in research and give their consent. If they are
deceived, what they DID consent to must be similar to
actual study. Minimize trauma.
 Anonymity/confidentiality/privacy
 Risk – mental and physical safety
 Debriefing procedure – afterward,
participants must be told of purpose of
study - need ability to contact researcher
about results.
What is the IV? DV?
 A researcher was interested in the effects of reward on
intrinsic motivation. Some children were told that they
would be given a special award for drawing with magic
markers (an activity they already enjoyed). Other
children were simply asked to draw with the magic
markers. One week later, the children were
unobtrusively observed for how much time they spent
drawing with the markers. The children who expected
and received a reward for drawing with the markers
were less likely to draw with them later.
 In an investigation of the fundamental attribution error, subjects
were given a speech to read that either favored or opposed Fidel
Castro, the communist leader of Cuba. Subjects were told that the
speech was written by a student who had been assigned to the
position taken in the paper (that is, the student writing the speech
had no choice on which position to take). Nevertheless, subjects
believed that the student who wrote the pro-Castro speech had
positive attitudes toward Castro, while subjects who read the antiCastro paper believed the writer had negative attitudes toward
 Within a classroom setting, subjects were asked to listen to a guest
instructor. All subjects were given a description of the instructor.
Some subjects read a description containing the phrase “People
who know him consider him to be a rather cold person...”, while
other people read a description where the word “warm” was
substituted for the word cold (otherwise, the descriptions were
identical). After the lecture, subjects were asked to rate the
instructor. Subjects who were told the instructor was warm gave
him more favorable ratings compared to subjects who were told
that the instructor was cold.
 Subjects watched a videotape of a woman taking an SAT-like
test. In all cases, she correctly answered 15 out of 30
questions. But subjects who observed a pattern of initial
success followed by failure perceived the woman as more
intelligent than did those who observed the opposite pattern
of failure followed by success.
 Subjects read about a woman who used a particular title, and
then rated her on a number of traits. When the woman used
the title Ms. rather than Miss or Mrs., she was assumed to be
more assertive, achievement oriented, and dynamic, but also
cold, unpopular, and unlikely to have a happy marriage
 People were randomly approached on the street by a stranger
and were asked to use his camera to take a picture of him for a
school project. For half of the subjects, the camera didn’t
work--the stranger looked concerned, said that the camera
was rather delicate, asked the subject if he touched any of the
dials, and announced that it would have to be fixed. For the
other half of the subjects, the camera worked fine. Further
down the street, a woman dropped a file folder of papers.
Forty percent of the subjects who had the working camera
experience helped the woman pick up her papers, while 80%
of the subjects who were led to believe that they broke the
woman’s camera helped.
Chapter 2 Quiz
The Research Enterprise in Psychology
Don’t forget to write your answers on a separate
piece of paper to grade when you’re done!
1. Organized sets of concepts that explain phenomena are
a) independent variables
b) dependent variables
c) hypotheses
d) theories
2. “Students will be able to read a statement printed in the
Comic Sans font faster than the same statement written in
the Lucida Calligraphy font.”
The previous statement is a(n)
a) hypothesis
b) theory
c) replication
d) operational definition
3. A theory is
a) a tentative statement about the
relationship between two or more
b) a system of interrelated ideas used
explain a set of observations
c) a statement of research results that
been proven to be correct
d) a preliminary proposal that has yet
to be
4. Theoretically, random assignment should eliminate
a) sampling error
b) the need to use statistics
c) concerns over validity
d) many confounding variables
5. When subjects in the experimental group put a puzzle
piece in the wrong place, the experimenter
unconsciously winced. The experimenter did not wince
when subjects in the control group put a piece in the
wrong place.
The wincing of the experimenter must be eliminated
because it is
a) fraudulent
b) a demand characteristic
c) a confabulation
d) a confounding variable
6. The two basic types of statistics are
a) descriptive and inferential
b) central tendency and variability
c) sampling and correlative
d) parametric and nonparametric
7. Of the following, which research method is most effective
for studying unusually complex or rare phenomena?
a) controlled experiment
b) surveys
c) naturalistic observation
d) case study
8. Of the following, which research method would be most
appropriate for investigating the relationship between
political party membership and attitude toward the death
a) controlled experiment
b) naturalistic observation
c) test
d) survey
9. Of the following, the strongest positive correlation would
most likely be shown between
a) an adult’s weight and running speed
b) close friendships and happiness
c) sense of humor and years of education
d) visual acuity and salary
10. John wants to study the effects of alcohol on the
behavior of college students. For his study, he spends 5
hours every night for 2 weeks at a bar near a college
watching how the patrons act before and after drinking
alcoholic beverages. The research method John is
employing is a
a) controlled experiment
b) survey
c) test
d) naturalistic observation
11. What is the median of the following distribution: 6, 2, 9,
4, 7, 3?
12. Of the following, the correlation coefficient that indicates
the strongest relationship between the two variables being
measured is
a) +0.65
b) -0.89
c) 0.00
d) +3.45
13. Inferential statistics help us determine whether ________
played a role in an experiment
a) chance
b) a dependent variable
c) a normal distribution
d) genetics
14. Placebo effects occur when
a) the sample is not representative of the
b) two variables are confounded
c) subjects are influenced by the social
desirability bias
d) due to their expectations, subjects
experience some change from a
nonexistent or
ineffective treatment
15. Which set of concepts is NOT a closely related set?
a) mean, median, mode
b) method, results, discussion
c) experiment, independent variable,
d) correlation, sample, journal
Chapter 2 Answer Key
1. D
2. A
3. B
4. D
5. D
6. A
7. D
8. D
9. B
10. D
Essay Question Possibilities!!
 One of the following essay questions will appear on your
test, be familiar with all of them!!
Essay Question # 1
 Design a simple experiment to investigate the effects of
television violence on children’s aggressive behavior, being
sure to identify the independent and dependent variables, and
the experimental and control groups.
Essay Question # 2
 Design a simple descriptive/correlational study to investigate
the relationship between television violence and children’s
aggressive behavior.