AP Statistics
NAME________________________________
Confounding/Common Response/Lurking Variable Exercises
Section 4-3
Use what you have learned in section 4-3 to answer the following questions.
1.) Measure the number of TVs per person x and the average life expectancy y for the world’s nations.
There is a high positive correlation: nations with many TVs have higher life expectancies. Could we
lengthen the lives of people in Rwanda by shipping them TVs?
2.) People who use artificial sweeteners in place of sugar tend to be heavier than people who use real
sugar. Does this mean that artificial sweeteners cause weight gain? Give a more plausible explanation
for this association.
3.) A study showed that women who work in the production of computer chips have a high number of
miscarriages. The union claimed exposure to chemicals causes the miscarriages. Another possible
explanation is that the workers spend their entire shift standing up. Can we conclude that exposure to
chemicals causes more miscarriages?
4.) A study once found that people with two cars live longer than people who own only one car.
Owning three cars is even better and so on. There is substantial positive correlation between the
number of cars x and the length of life y. What lurking variables might explain the association?
5.) Children who watch many hours of TV get lower grades in school on the average than those who
watch less TV. Suggest some other variables that may be confounded with heavy TV watching and
may contribute to poor grades.
6.) Data show that men, who are married, and also divorced or widowed men, earn quite a bit more
than men the same age who have never been married. Does this mean that getting married can increase
your salary?
7.) A study finds that HS students, who take the SAT, enroll in an SAT course, and then take the SAT
a second time raise their SAT math score from a mean of 521 to 561. What factors other than taking
the course might explain this improvement.
8.) People who do well tend to feel good about themselves do better in school than those people who
do not. Can you think of explanations for the association between high self-esteem and good school
performance?
9.) There is a negative correlation between the number of flu cases reported each week throughout the
year and the amount of ice cream sold in that particular week. Does ice cream prevent the flu?