A large sample of students was surveyed at a particular university. Among other things, they were asked to report their weight, and how many minutes of television they had watched the day before.
a. Give at least two reasons why we can expect the relationship between weight and TV time to be positive.
b. If weight is taken to be the explanatory variable, what would this be suggesting in particular about weight and TV time?
c. If TV time is taken to be the explanatory variable, what would this be suggesting in particular about weight and TV time?
d. Explain why gender should be taken into account as a possible confounding variable.
e. Use software to separate out the weights and TV times of males from females. Regress weight on TV time for each gender group, and report the value of the correlation r and the P-value for males and for females, testing against the onesided alternative b1 <>
f. Although the correlations are practically identical, one of the P-values is considerably smaller than the other. What is the simplest explanation for how this came about?
g. Do your regression results suggest that, in general, watching more TV causes students to gain weight? Explain. h. Do your regression results suggest that, in general, students who watch more TV tend to weigh more? Explain.