Supplement test. A pharmaceutical company is producing and marketing a vitamin supplement to help fight infections.

In an experiment to test the product, subjects were assigned randomly to take the vitamin supplement or a placebo. The number of days of illness from infections was recorded. Here are boxplots comparing the two groups, followed by some computer output from a two-sample t-test computed for the data.

2-Sample t-Test of mS - mp … 0 Difference Between Means = -2.83 t-Statistic = -2.40 w/94 df P = 0.0091

a) What does the P-value mean in this context?

b) What is your conclusion about the effectiveness of the supplement?

c) Opponents of vitamin supplements continue to insist that they are useless. What type of error do they claim your conclusion makes?

Transcribed Image Text:

40 40 20 * 0 Supplement Placebo