MATH 1342. Chapters 1 and 2. (2 days)
Mary Parker. January 2013
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Day 2 of Chapters 1 and 2.
Activity 1. Do this activity with a partner. A study of 74 seventeen-year-old girls asked them how many
servings of fruit a day they eat, on the average. Here is a histogram of the data. (Moore text, exercise 1.30)
1.a. Estimate the center (the score that half
the girls score below and half score above.)
1.b. Count and find precisely what score that
center is.
1.c. What percentage of the girls at fewer
than two servings a day?
1.d. What percentage of the girls ate two or
fewer servings a day?
Do any of these scores look as if they are
outliers?
1.e. Explain what numbers you would have to type into the software to compute summary statistics of these
scores. (You do not have to actually type them in – just explain how you know what the numbers are.)
1.f. Find the quartiles and the InterQuartile Range of this distribution without typing them in – just by counting
as you did when you found the median.
1.g. According to our text’s definition of “Suspected Outliers” in Chapter 2, are any of these scores outliers?
(Show your work as well as answer the question.)
Activity 2. Standard deviation. Download the Excel spreadsheet provided by the teacher:
http://www.austincc.edu/mparker/stat-general/ named stdev.xls. Make up six numbers and guess their
standard deviation. Then type in the six numbers into the yellow cells of the “six” worksheet. How close was
your guess to that standard deviation? (It doesn’t have to be very close – just “in the ballpark.”) See what
numbers your partner used. Discuss. (It doesn’t have to be very close – just “in the ballpark.” I won’t really
test you on this guessing. This is about understanding the concept.)
Activity 3. With a partner, answer 2.12 at the end of the section “Choosing a measure of center and spread.”
Activity 4. With a partner, do Exercise 2.13 in “Organizing a Statistical Problem”.
MATH 1342. Chapters 1 and 2. (2 days)
Mary Parker. January 2013
page 2 of 3
After the second, and final, class on Chs 1 and 2:
1. From any frequency graph (not a relative frequency graph) be able to “reconstruct” the dataset, as
much as the information allows.
2. By hand and with software, compute all the numerical summaries indicated in the given table in this
handout. When computing median and quartiles by hand,
a. in the first step, sort the data. (If the dataset has more than about six values, making a first
draft of a stemplot by hand is helpful to begin.)
b. correctly use
n 1
several times.
2
c. consider the values below, not including, the median when finding Q1, etc.
d. recognize that software may use a more sophisticated formula for medians and quartiles and
so the software values for these may differ from what you found by hand, or from what
another software package obtained.
3. Use the IQR rule to identify “suspected outliers.”
4. Boxplots. Sometimes software does not extend the “whiskers” all the way out to the maximum and
minimum. When it does not, and puts extra dots beyond the “whiskers” that means those are
suspected outliers, according to some rule like the 1.5*IQR rule. (Example: Minitab, Parker dataset
Fish_prices.txt .)
5. Standard deviation:
a. Recognize that Example 2.7 which shows how to compute a standard deviation, is given to
show you what we mean by “the amount a typical score differs from the mean” and is NOT to
show how you are supposed to compute standard deviation. DO NOT compute standard
deviations in that way. It takes too long and you need your time for learning more important
things.
b. When given a frequency graph which is not strongly skewed, estimate the mean and make
some reasonable statements about what values would be unreasonably small or unreasonably
large as estimates of the standard deviation. (The mean is approximately ___ and the
standard deviation surely must be between ___ and ____. (This doesn’t have to be a very
“tight” interval – just enough to show that you know that the standard deviation is “the
amount a typical score differs from the mean.”
6. Identify and use the four steps of the four-step process to answer questions about comparing the
distributions of a variable on two or more groups, including discussing the meaning of any differences
you see.
MATH 1342. Chapters 1 and 2. (2 days)
Mary Parker. January 2013
page 3 of 3
Quiz 3. Due Wed. Feb. 6 at the beginning of class.
Exercise 1.32. Do parts a-d using just the information given in the exercise and the graph, without looking at
the full dataset. Then, using the full dataset and software to find the quartiles, answer part e as given just
below here.
e. Find the quartiles and use our rule to determine whether data points they called outliers are
identified as “suspected outliers”. Show your work. (It is not necessary to provide printed output
here. Just say what relevant values you obtained from the software and use them.)
Exercise 2.46. Write something for each part of the four-step process. It is not necessary to re-write the entire
problem in the “State” part. Just say what you are asked to do (two sentences here.) Use Minitab for graphs
and computations and provide a printout of your results, as well as summarize them in your written answers.
Exercise 4.26. Before you make a graph, identify the response variable and the explanatory variable. Use
Minitab for graphs and computations and include a printout of the graph in your results. You may just say
what you found with software for the correlation coefficient without providing a printout of the results from
the software.
Exercise 4.38. No computation. Answer this question in writing.