Two random samples were selected independently from populations having normal distributions. The following statistics were extracted from the samples:

x 1  42.3 –x 2  32.4

a. If s1  3 and s2  2 and the sample sizes are n1  50 and n2  50, calculate a 95% confidence interval for the difference between the two population means.

b. If s1  s2, s1  3, and s2  2, and the sample sizes are n1  10 and n2  10, calculate a 95%
confidence interval for the difference between the two population means.

c. If s1  s2, s1  3, and s2  2, and the sample sizes are n1  10 and n2  10, calculate a 95%
confidence interval for the difference between the two population means.