# Question

Refer to Exercise 10.28. Now assume that the two populations are normally distributed with unequal and unknown population standard deviations.

In Exercise 28

a. Make a 90% confidence interval for the difference between the corresponding population means.

b. Test at a 5% significance level whether the two population means are different.

c. Suppose that the sample standard deviations were 9.5 and 5.1 hours, respectively. Redo parts a and b. Discuss any changes in the results.

In Exercise 28

a. Make a 90% confidence interval for the difference between the corresponding population means.

b. Test at a 5% significance level whether the two population means are different.

c. Suppose that the sample standard deviations were 9.5 and 5.1 hours, respectively. Redo parts a and b. Discuss any changes in the results.

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