Question

Find the 95% confidence interval for the difference between two means based on this information about two samples. Assume independent samples from normal populations. (Use conservative degrees of freedom.) (Give your answers correct to two decimal places.)

Sample	Number	Mean	Std. Dev.
1	17	40	26
2	30	26	27

Lower Limit
Upper Limit

You may need to use the appropriate table in Appendix B to answer this question.

Answer 1

Formula for Confidence Interval for Difference in two Population means when population Standard deviation are not known (non pooled)

(Conservative)

n1 : Sample Size of Sample 1	17
n2 : Sample Size of Sample 2	30
: Sample Mean of Sample 1	40
: Sample Mean of Sample 2	26
s1 : Sample Standard Deviation of Sample 1	26
s2 : Sample Standard Deviation of Sample 2	27
Confidence Level	95%
\alpha (= 100-95/100=5/100 ) = 0.05	0.05
\alpha/2 (=0.05/2=0.025)	0.025
Degrees of Freedom : =Min(17-1,30-1)	16
	2.1199

95% confidence interval for the difference between two means

Lower Limit - 2.97

Upper Limit 30.97