13.8 random sampling from two normal populations produced the

  

13.8 Random sampling from two normal populations produced the following results:
X-bar1 = 412 s1 = 128 n1 = 150
X-bar2 = 405 s2 = 54 n2 = 150
 

a. Can we infer at the 5% significance level that μ1 is greater than μ2?
b. Repeat part (a) decreasing the standard deviations to s1 = 31 and s2 = 16.
c. Describe what happens when the sample standard deviations get smaller.
d. Repeat part (a) with samples of size 20.
e. Discuss the effects of decreasing the sample size.
f. Repeat part (a) changing the mean of sample 1 to 409
g. Discuss the effect of decreasing.