A pharmaceutical manufacturer wants to investigate the bioactivity of a new drug. A completely randomized single-factor experiment was conducted with three dosage levels, and the following results were obtained.

Dosage Observations
20g 24 28 37 30
30g 37 44 31 35
40g 42 47 52 38

a. Is there evidence to indicate that dosage level affects bioactivity? Use α = 0.05.
b. If it is appropriate to do so, make comparisons between the pairs of means. What conclusions can you draw?
c. Analyze the residuals from this experiment and comment on adequacy.