Table 7.17 summarizes the number of hours spent in laboratory per week by researchers, based on a recent study.

(a) Estimate the difference between population means for junior and senior fellows.

(b) Show that the estimated standard error of the sample difference is 0.58.

Interpret.

(c) Show that a 99% confidence interval for the difference is (0.51, 3.49). Interpret.

TABLE 7.17 Laboratory Hours Research fellow Sample Size Mean Standard Deviation Junior 415 5.5 8.2 Senior 560 7.5 9.8