Question

Random samples of female and male UVA undergraduates are asked to estimate the number of alcoholic drinks that each consumes on a typical weekend. The data is below: Females (Population 1): 2, 4, 4, 5, 4, 3, 5, 4, 2, 2 Males (Population 2): 8, 9, 6, 9, 9, 5, 5, 7, 8, 8 Give a 91.6% confidence interval for the difference between mean female and male drink consumption. (Assume that the population variances are equal.) Confidence Interval =

Answer 1

Ans:

df=10+10-2=18

t*=TINV(0.084,18)=1.829

	Females	Males
1	2	8
2	4	9
3	4	6
4	5	9
5	4	9
6	3	5
7	5	5
8	4	7
9	2	8
10	2	8
mean	3.5	7.4
std. dev.	1.1785	1.5776

Point estimate=3.5-7.4=-3.9

standard error for difference=sqrt((1.1785^2/10)+(1.5776^2/10))=0.6227

91.6% confidence interval for the difference between mean female and male drink consumption

=-3.9+/-1.829*0.6227

=-3.9+/-1.139

=(-5.039, -2.761)