Question

A drug company is analyzing the effectiveness of a cholesterol reducing medication. A random sample of 9 subjects with high cholesterol were tested before and after three weeks of treatment with the drug and data appears in the table below. Assume cholesterol levels are normal. Find a 90% confidence interval for the mean difference in cholesterol level after treatment. What is the margin of error and confidence interval?

Level before: 177   169   173   174   180   179   184   171   185
Level after: 156   138   140   161   146   159   137   154   139

Answer 1

The table given below ,

Level before(X)	Level after(Y)	d-=X-Y	di^2
177	156	21	441
169	138	31	961
173	140	33	1089
174	161	13	169
180	146	34	1156
179	159	20	400
184	137	47	2209
171	154	17	289
185	139	46	2116
	Sum	262	8830

From table,

Now ,

Therefore , the 90% confidence interval for the mean difference in cholesterol level is ,