Male female democrat 300 600 republican 500 300 other

Male Female
Democrat 300 600
Republican 500 300
Other 200 100

8. Mr. Yates picked up a dozen items in the grocery store with a mean cost of $3.25. Then he
added an apple pie for $6.50. The new mean for all 13 items is
9. A small company estimating its photocopying expenses finds that the mean number of copies
made per day for the past 12 months is 258 copies per day with a standard deviation of 24
copies per day. Which of the following is a correct interpretation of standard deviation?
10. The five-number summary for scores on a statistics exam is 11, 35, 61, 70, 79. In all, 380
students took the test. About how many had scores between 35 and 61?
36 The Practice of Statistics, 4/e- Chapter 1 © 2011 BFW Publishers

© 2011 BFW Publishers The Practice of Statistics, 4/e- Chapter 1 37
Part 2: Free Response
Show all your work. Indicate clearly the methods you use, because you will be graded on the
correctness of your methods as well as on the accuracy and completeness of your results and
explanations.
Nitrates are organic compounds that are a substantial component of agricultural fertilizers.
When those fertilizers run off into streams, the nitrates can have a toxic effect on animals that
live in those streams. An ecologist studying nitrate pollution in two streams collects data on
nitrate concentrations at 42 places on Stony Brook and 42 places on Mill Brook. His results are
given in the dotplots and computer output below.
Total
Variable Count Mean SE Mean StDev Minimum Q1 Median Q3
Stony Brook 42 5.524 0.451 2.922 0.000 3.500 5.000 7.500
Mill Brook 42 7.929 0.711 4.607 0.000 4.500 8.250 10.500
11. Determine if there are any outliers in each distribution. Show your work.
12. Draw parallel boxplots of these two distributions. Be sure to label the plots and provide a
scale.
13. Write a few sentences comparing the nitrate concentrations in Stony Brook and Mill Brook.
Maximum
12.000
20.000

38 The Practice of Statistics, 4/e- Chapter 1 © 2011 BFW Publishers
The following data represent scores of 34 students on a calculus test.
72 59 73 72 74 74 61
72 78 80 57 56 76 72
88 74 57 83 68 79
70 65 67 76 67 72
14. Construct a histogram for this distribution. Choose an appropriate bin width, and be sure to
provide a label and scale for each axis.
15. Based on your histogram, what numerical measures of center and spread would be best to
use for this distribution? Explain your choice.
67 67
54 65
73 71
76 53

© 2011 BFW Publishers The Practice of Statistics, 4/e- Chapter 1 39
In a study of the relationship between the amount of violence a person watches on TV and the
viewer’s age, 81 regular TV watchers were randomly selected and classified according to their
age group and w