A research would like to examine the effects of humidity on eating behavior. It is known that laboratory rats normally eat an average of µ = 21 grams of food each day. The research selects a random sample of n = 16 rats and places them in a controlled atmosphere room in which the relative humidity is maintained at 90%. The daily food consumption scores for rats are as follows:

14, 18, 21, 15, 18, 18, 21, 18
16, 20, 17, 19, 20, 17, 17, 19

a) Can the researcher conclude that humidity has a significant effect on eating behavior? Use a two-tail test with α = .05.

b) Compute the estimated Cohen's d and r2 to measure the size of the treatment effect.