2 Refer to Table 6.2 and Example 6 7. Table 7.9 is a computer printout that summarizes the responses on the seven-point poliucal ideology scale for the surveys in 1978 and in 1994.

a) Are these samples independent or dependent?

b) Construct a 95% confidence interval for the difference between the mean political ide- ology in 1994 and 1978 Interpret.

c) Show how to test the hypothesis that the population mean political ideology was equal in 1978 and 1994. against the alterative of a difference. Report the P-value. and inter- pret.

d) Show the correspondence between the results of the inferences in

(b) and

(c) Which inference is more informative? Explain. TABLE 7.9 Variable: IDEOLOGY YEAR 1978 1994 N Mean Std Dev Std Error 627 4.03 1.26 .0503 2879 4.17 1.39 .0259 Variances T Prob>|T| Unequal 2.474 0.0134