SOLUTIONS MANUAL
ESSENTIALS OF STATISTICS
7TH EDITION
CHAPTER NO. 01. INTRODUCTION TO STATISTICS
SECTION 1-1: STATISTICAL AND CRITICAL THINKING
1. The respondents are a voluntary response sample or a self-selected sample. Because those with
strong interests in the topic are more likely to respond, it is very possible that their responses do
not reflect the opinions or behavior of the general population.
2. a. The sample consists of the 1046 adults who were surveyed. The population consists of
all adults.
b. When asked, respondents might be inclined to avoid the shame of the unhealthy habit of
not washing their hands, so the reported rate of 70% might well be much higher than it is
in reality. It is generally better to observe or measure human behavior than to ask subjects
about it.
3. Statistical significance is indicated when methods of statistics are used to reach a conclusion
that a treatment is effective, but common sense might suggest that the treatment does not make
enough of a difference to justify its use or to be practical. Yes, it is possible for a study to have
statistical significance, but not practical significance.
4. No. Correlation does not imply causation. The example illustrates a correlation that is clearly
not the result of any interaction or cause effect relationship between per capita consumption of
margarine and the divorce rate in Maine.
5. Yes, there does appear to be a potential to create a bias.
6. No, there does not appear to be a potential to create a bias.
7. No, there does not appear to be a potential to create a bias.
8. Yes, there does appear to be a potential to create a bias.
9. The sample is a voluntary response sample and has strong potential to be flawed.
10. The samples are voluntary response samples and have potential for being flawed, but this
approach might be necessary due to ethical considerations involved in randomly selecting subjects
and somehow imposing treatments on them.
11. The sampling method appears to be sound.
,12. The sampling method appears to be sound.
13. The Ornish weight loss program has statistical significance, because the results are so unlikely
(3 chances in 1000) to occur by chance. It does not have practical significance because the amount
of lost weight (3.3 lb) is so small.
14. Because there is only one chance in a thousand of getting such success rates by chance, the
difference does appear to have statistical significance. The 92% success rate for surgery appears
to be substantially better than the 72% success rate for splints, so the difference does appear to
have practical significance.
15. The difference between Mendel’s 25% rate and the result of 26% is not statistically significant.
According to Mendel’s theory, 145 of the 580 peas would have yellow pods, but the results
consisted of 152 peas with yellow
pods. The difference of 7 peas with yellow pods among the 580 offspring does not appear to be
statistically significant. The difference does not appear to have practical significance.
16. Because there is a 25% chance of getting such results with a program that has no effect, the
program does not appear to have statistical significance. Because the average increase is only 3 IQ
points, the program does not appear to have practical significance.
17. With 40 out of 41 ballots having the Democrat first, it appears that the result is statistically
significant. Because of the great advantage enjoyed by Democrats, the results also have practical
significance.
18. Because it is so unlikely (0.3%) to get these results by chance, the results have statistical
significance. With about 57% (from 235/414) of the coin toss winners going on to win the game,
the result appears to have practical significance.
19. There appears to be statistical significance given the large discrepancy between 79.1% and
39%. Because the results are so far from yielding a jury of peers, it appears that the results have
practical significance.
20. With only a 0.0000006% chance of getting such results, it appears that the results are
statistically significant. The discrepancy between the 61% rate for voters who actually did vote
and the 70% rate of those who said that they voted is a fairly large discrepancy, and the results
appear to have practical significance.
21. Yes. Each column of 8 AM and 12 AM temperatures is recorded from the same subject, so
each pair is matched.
,22. No. The source is from university researchers who do not appear to gain from distorting the
data.
23. The data can be used to address the issue of whether there is a correlation between body
temperatures at 8 AM and at 12 AM. Also, the data can be used to determine whether there are
differences between body temperatures at 8 AM and at 12 AM.
24. Because the differences could easily occur by chance (with a 64% chance), the differences do
not appear to have statistical significance.
25. No. The lemon imports are weights in metric tons and the crash fatality rates are fatalities per
100,000
population, so their differences are meaningless.
26. The issue that can be addressed is whether there is a correlation, or association, between lemon
imports and crash fatality rates.
27. No. The author of an article for the Journal of Chemical Information and Modeling has no
reason to collect or present the data in a way that is biased.
28. No. Correlation does not imply causation, so a statistical correlation between lemon imports
and crash fatality rates should not be used to conclude that lemon imports are the cause of fatal
crashes.
29. It is questionable that the sponsor is the Idaho Potato Commission and the favorite vegetable
is potatoes.
30. The sample is a voluntary response sample, so there is a good chance that the results do not
reflect the larger population of people who have a water preference.
31. The correlation, or association, between two variables does not mean that one of the variables
is the cause of the other. Correlation does not imply causation. Clearly, sour cream consumption
is not directly related in any way to motorcycle fatalities.
32. The sponsor of the poll is an electronic cigarette maker, so the sponsor does have an interest
in the poll results. The source is questionable.
33. The correlation, or association, between two variables does not mean that one of the variables
is the cause of the other. Correlation does not imply causation.
34. The correlation, or association, between two variables does not mean that one of the variables
is the cause of the other. Correlation does not imply causation.
, 35. The sample is a voluntary response sample, so there is a good chance that the results do not
accurately reflect the larger population.
36. Because the nutritionists are paid such large amounts of money, they might be more inclined
to find favorable results. It is very possible that the results represent desired outcomes instead of
actual outcomes.
37. a. 700 adults
b. 55%
38. a. 253.31 subjects
b. No. Because the result is a count of people among the 347 who were surveyed, the result
must be a whole number.
c. 253 subjects
d. 32%
39. a. 559.2 respondents
b. No. Because the result is a count of respondents among the 1165 engaged or married
women who were surveyed, the result must be a whole number.
c. 559 respondents
d. 8%
40. a. 847.56 drivers
b. No. Because the result is a count of respondents saying that they text while driving, the
result must be a whole number.
c. 848 drivers
d. Given that texting while driving is extremely dangerous, the result of 42% of drivers
who text while driving is far too high. The result suggests that steps should be taken to
substantially lower that rate.
41. Because a reduction of 100% would eliminate all of the size, it is not possible to reduce the
size by 100% or more.
42. In an editorial criticizing the statement, the New York Times correctly interpreted the 100%
improvement to mean that no baggage is being lost, which was not true.
43. Because a reduction of 100% would eliminate all plaque, it is not possible to reduce it by more
than 100%.
ESSENTIALS OF STATISTICS
7TH EDITION
CHAPTER NO. 01. INTRODUCTION TO STATISTICS
SECTION 1-1: STATISTICAL AND CRITICAL THINKING
1. The respondents are a voluntary response sample or a self-selected sample. Because those with
strong interests in the topic are more likely to respond, it is very possible that their responses do
not reflect the opinions or behavior of the general population.
2. a. The sample consists of the 1046 adults who were surveyed. The population consists of
all adults.
b. When asked, respondents might be inclined to avoid the shame of the unhealthy habit of
not washing their hands, so the reported rate of 70% might well be much higher than it is
in reality. It is generally better to observe or measure human behavior than to ask subjects
about it.
3. Statistical significance is indicated when methods of statistics are used to reach a conclusion
that a treatment is effective, but common sense might suggest that the treatment does not make
enough of a difference to justify its use or to be practical. Yes, it is possible for a study to have
statistical significance, but not practical significance.
4. No. Correlation does not imply causation. The example illustrates a correlation that is clearly
not the result of any interaction or cause effect relationship between per capita consumption of
margarine and the divorce rate in Maine.
5. Yes, there does appear to be a potential to create a bias.
6. No, there does not appear to be a potential to create a bias.
7. No, there does not appear to be a potential to create a bias.
8. Yes, there does appear to be a potential to create a bias.
9. The sample is a voluntary response sample and has strong potential to be flawed.
10. The samples are voluntary response samples and have potential for being flawed, but this
approach might be necessary due to ethical considerations involved in randomly selecting subjects
and somehow imposing treatments on them.
11. The sampling method appears to be sound.
,12. The sampling method appears to be sound.
13. The Ornish weight loss program has statistical significance, because the results are so unlikely
(3 chances in 1000) to occur by chance. It does not have practical significance because the amount
of lost weight (3.3 lb) is so small.
14. Because there is only one chance in a thousand of getting such success rates by chance, the
difference does appear to have statistical significance. The 92% success rate for surgery appears
to be substantially better than the 72% success rate for splints, so the difference does appear to
have practical significance.
15. The difference between Mendel’s 25% rate and the result of 26% is not statistically significant.
According to Mendel’s theory, 145 of the 580 peas would have yellow pods, but the results
consisted of 152 peas with yellow
pods. The difference of 7 peas with yellow pods among the 580 offspring does not appear to be
statistically significant. The difference does not appear to have practical significance.
16. Because there is a 25% chance of getting such results with a program that has no effect, the
program does not appear to have statistical significance. Because the average increase is only 3 IQ
points, the program does not appear to have practical significance.
17. With 40 out of 41 ballots having the Democrat first, it appears that the result is statistically
significant. Because of the great advantage enjoyed by Democrats, the results also have practical
significance.
18. Because it is so unlikely (0.3%) to get these results by chance, the results have statistical
significance. With about 57% (from 235/414) of the coin toss winners going on to win the game,
the result appears to have practical significance.
19. There appears to be statistical significance given the large discrepancy between 79.1% and
39%. Because the results are so far from yielding a jury of peers, it appears that the results have
practical significance.
20. With only a 0.0000006% chance of getting such results, it appears that the results are
statistically significant. The discrepancy between the 61% rate for voters who actually did vote
and the 70% rate of those who said that they voted is a fairly large discrepancy, and the results
appear to have practical significance.
21. Yes. Each column of 8 AM and 12 AM temperatures is recorded from the same subject, so
each pair is matched.
,22. No. The source is from university researchers who do not appear to gain from distorting the
data.
23. The data can be used to address the issue of whether there is a correlation between body
temperatures at 8 AM and at 12 AM. Also, the data can be used to determine whether there are
differences between body temperatures at 8 AM and at 12 AM.
24. Because the differences could easily occur by chance (with a 64% chance), the differences do
not appear to have statistical significance.
25. No. The lemon imports are weights in metric tons and the crash fatality rates are fatalities per
100,000
population, so their differences are meaningless.
26. The issue that can be addressed is whether there is a correlation, or association, between lemon
imports and crash fatality rates.
27. No. The author of an article for the Journal of Chemical Information and Modeling has no
reason to collect or present the data in a way that is biased.
28. No. Correlation does not imply causation, so a statistical correlation between lemon imports
and crash fatality rates should not be used to conclude that lemon imports are the cause of fatal
crashes.
29. It is questionable that the sponsor is the Idaho Potato Commission and the favorite vegetable
is potatoes.
30. The sample is a voluntary response sample, so there is a good chance that the results do not
reflect the larger population of people who have a water preference.
31. The correlation, or association, between two variables does not mean that one of the variables
is the cause of the other. Correlation does not imply causation. Clearly, sour cream consumption
is not directly related in any way to motorcycle fatalities.
32. The sponsor of the poll is an electronic cigarette maker, so the sponsor does have an interest
in the poll results. The source is questionable.
33. The correlation, or association, between two variables does not mean that one of the variables
is the cause of the other. Correlation does not imply causation.
34. The correlation, or association, between two variables does not mean that one of the variables
is the cause of the other. Correlation does not imply causation.
, 35. The sample is a voluntary response sample, so there is a good chance that the results do not
accurately reflect the larger population.
36. Because the nutritionists are paid such large amounts of money, they might be more inclined
to find favorable results. It is very possible that the results represent desired outcomes instead of
actual outcomes.
37. a. 700 adults
b. 55%
38. a. 253.31 subjects
b. No. Because the result is a count of people among the 347 who were surveyed, the result
must be a whole number.
c. 253 subjects
d. 32%
39. a. 559.2 respondents
b. No. Because the result is a count of respondents among the 1165 engaged or married
women who were surveyed, the result must be a whole number.
c. 559 respondents
d. 8%
40. a. 847.56 drivers
b. No. Because the result is a count of respondents saying that they text while driving, the
result must be a whole number.
c. 848 drivers
d. Given that texting while driving is extremely dangerous, the result of 42% of drivers
who text while driving is far too high. The result suggests that steps should be taken to
substantially lower that rate.
41. Because a reduction of 100% would eliminate all of the size, it is not possible to reduce the
size by 100% or more.
42. In an editorial criticizing the statement, the New York Times correctly interpreted the 100%
improvement to mean that no baggage is being lost, which was not true.
43. Because a reduction of 100% would eliminate all plaque, it is not possible to reduce it by more
than 100%.
