Section 2.5 Solutions

2.84

Students who take online courses may also be working full-time jobs. Hence, they may be more motivated to learn the material (because it applies directly to their work) and they may have more work experiences that help them learn the material. These are just two of many possible confounding variables.

2.86

If a company has more employees, then obviously there are more employees to lay off. Also, a large company probably pays its CEO more (since there is presumably more work involved in running a large company). The opposite is true for small companies. Hence, the relationship between layoff size and CEO pay can possibly be explained by a common response to the size of the company.

2.88

If a nation has a high income per capita, then its citizens (on average) have money to spend on things that help their health (e.g., health care, healthful food, gym memberships, medicine). Hence, high income per capita can cause better health.

On the other hand, if a nation’s people are healthy, then they can work more hours, put more energy into the jobs, miss less work due to illness, which may lead to higher per capita income.

2.90

Some possible variables that may be confounded with whether students took the course are

· the fact the students took the SAT a second time, and may have in fact learned from the first time;

· the students may study/prepare for the SAT exam more the second time around (since they did poorly the first time);

· The students may be learning material in other high school courses that applies to the SAT.

2.93

There are definitely variables that are confounded with heavy TV viewing and may contribute to poor grades. For example, time spent with parents, education of parents, attention level of student, motivation level of student, etc.