91Ó°ÊÓ

An analyst in a large corporation studied the relation between current annual salary ( \(Y\) ) and age \((X)\) for the 46 computer programmers presently employed in the company. The analyst concluded that the relation is curvilinear, reaching a maximum at 47 years. Does this imply that the salary for a programmer increases until age 47 and then decreases? Explain.

In a study of the relationship for senior citizens between physical activity and frequency of colds, participants were asked to monitor their weekly time spent in exercise over a five-year period and the frequency of colds. The study demonstrated that a negative statistical relation exists between time spent in exercise and frequency of colds. The investigator concluded that increasing the time spent in exercise is an effective strategy for reducing the frequency of colds for senior citizens. a. Were the data obtained in the study observational or experimental data? b Comment on the validity of the conclusions reached by the investigator c. Identify two or three other explanatory variables that might affect both the time spent in exercise and the frequency of colds for senior citizens simulianeously. d. How might the study be changed so that a valid conclusion about causal relationship between amount of exercise and frequency of colds can be reached?