9 the weights of the male and female students in a

9. The weights of the male and female students in a class are summarized in the following
boxplots:
Which of the following is NOT correct?
(a) About 50% of the male students have weights between 150 and 185 pounds.
(b) About 25% of female students have weights above 130 pounds.
(c) The median weight of male students is about 162 pounds.
(d) The mean weight of female students is about 120 pounds.
(e) The male students have less variability than the female students.
10. When testing water for chemical impurities, results are often reported as bdl, that is, below
detection limit. The following are the measurements of the amount of lead in a series of
water samples taken from inner-city households (in parts per million):
5, 7, 12, bdl, 10, 8, bdl, 20, 6
Which of the following statements can we be sure is true?

44 The Practice of Statistics, 4/e- Chapter 1 © 2011 BFW Publishers
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.
The states differ greatly in the kinds of severe weather that afflict them. The histogram below
shows the distribution of average annual property damage caused by tornadoes over the period from
1950 to 1999 in the 50 United States. (To adjust for the changing buying power of the dollar over
time, all damages were restated in 1999 dollars.)
11. Describe the important features of this distribution. What does this tell you about how the
economic burden of tornados is distributed among the states?
12. When asked for summary statistics, MINITAB produced the following output:
Variable N Mean SE Mean StDev Minimum Q1 Median Q3
Damage 50 22.39 3.60 25.45 0.00 2.23 12.66 41.63
Give the five-number summary, and explain why you can see from these five numbers that the
distribution is strongly skewed to the right.
13. The histogram suggests that there may be outliers. Use the 1.5 x IQR rule of thumb to show that
no values in this distribution meet this criterion for outliers.
90 80 70 60 50 40 30 20 10 0
25
20
15
10
5
0
Average annual tornado damage, $millions
Number of states
Maximum
88.60

© 2011 BFW Publishers The Practice of Statistics, 4/e- Chapter 1 45
Below are the lengths, in minutes, of the 25 most popular movies, as voted on by visitors to a
web site devoted to movies.
142 195 201 139
175 96 121 130
200 133 102 178
161 124 146 115
154 152 207 112
14. Make a stemplot of these data.
15. The mean of this distribution is 144.7 and the median is 139. Explain why you could have
predicted that the mean would be higher than the median by looking at the stemplot.
106
109
165
118
136