A random sample of 40 men drank an average of 20 cups of coffee per week during finals, while a sample of 30 women drank an average of 15 cups of coffee per week. The sample standard deviations were 6 cups for the men and 3 cups for the women. The standard error for the difference between the two sample means is 1.095. Calculate an approximate 95% confidence interval for the difference in average cups of coffee drunk (men -women).
A) (2.81, 7.19)
B) (3.02, 6.98)
C) (3.91, 6.10)
D) None of the above

Question

Quizplus · Accepted Answer

The difference in sample means is 5 cups (20 - 15). The 95% confidence interval is calculated as the difference in means ± 1.96 * standard error. Thus, 5 ± 1.96 * 1.095 = (2.85, 7.15), which rounds to (2.81, 7.19).

A Random Sample of 40 Men Drank an Average of 20