Question

An experiment was conducted to evaluate the effectiveness of a treatment for tapeworm in the stomachs of sheep. A random sample of 24 worm-infected lambs of approximately the same age and health was randomly divided into two groups. Twelve of the lambs were injected with the drug and the remaining twelve were left untreated. After 6 months, the lambs were slaughtered and the following worm counts were recorded. Assume the counts are approximately normally distributed.

Drug-treated sheep	18	43	28	50	16	32	13	35	38	33	6	7
untreated sheep	40	54	26	63	21	37	39	23	48	58	23	39

(a) Construct a 98% confidence interval for the difference of the worm count in a lamb.

(b) Please perform a statistical test and see if the drug treatment reduced the mean worm count in a lamb. Use the significance level 0.05.

(c) What are your assumptions that you assumed in part (b)?

Answer 1