A 1991 survey of 47 college sophomores investigated the relationship between the amount of time spent studying and one’s grades. A least squares regression gave these results:

where Y = grade point average on a 4-point scale, X = average hours per week spent studying, and the standard errors are in parentheses.

a. Does the estimated equation indicate that more studying leads to higher or lower grades?

b. Is the relationship statistically significant at the 5 percent level?

c. The average grade point average in this sample was 3.296; what is the average number of hours per week spent studying?

d. This researcher assumed that grade point average is the dependent variable and studying is the explanatory variable. Could it possibly be the other way around?

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Y 2.945 +0.2022X, (0.100) (0.006) R = 0.26