Refer to the brain NE data of Example 7.2.1. Suppose you are planning a similar experiment; you will study the effect of LSD (rather than toluene) on brain NE. You anticipate using a two-tailed t test at a = 0.05. Suppose you have decided that a 10% effect (increase or decrease in mean NE) of LSD would be important, and so you want to have good power (80%) to detect a difference of this magnitude.
(a) Using the data of Example 7.2.1 as a "pilot study," determine how many rats you should have in each group. (The mean NE in the control group in Example 7.2.1 is 444.2 ng/g and the SD is = 69.6 ng/g.)
(b) If you were planning to use a one-tailed / test, what would be the required number of rats?
Example 7.2.1
For each of the following data sets, use Table 4 to bracket the two-tailed P-value of the data as analyzed by the t test.
(a)

(b)

(c)

Sample 1 Sample 2 4 735 SE(x,-%) = 38 with df = 4 854 Sample 1 Sample 2 71 5.3 5.0 SE( 0.24 with df 12 Sample 1Sample 2 15 36 20 30 SEY-Y1.3 with df 30