Using techniques from an earlier section, we can find a confidence interval for _d. Consider a random sample of n matched data pairs A, B. Let d = BA be a random variable representing the difference between the values in a matched data pair. Compute the sample mean dof the differences and the sample standard deviation s_d. If d has a normal distribution or is mound-shaped, or if n 30, then a confidence interval for _d is as follows. dE < _d < d + E

where E = t_c

s_d

c = confidence level (0 < c < 1)

t_c = critical value for confidence level c and d.f. = n1

B: Percent increase for company	10	30	30	18	6	4	21	37
A: Percent increase for CEO	23	26	28	14	4	19	15	30

(a) Using the data above, find a 95% confidence interval for the mean difference between percentage increase in company revenue and percentage increase in CEO salary. (Round your answers to two decimal places.)

lower limit
upper limit

(b) Use the confidence interval method of hypothesis testing to test the hypothesis that population mean percentage increase in company revenue is different from that of CEO salary. Use a 5% level of significance.

Since _d = 0 from the null hypothesis is in the 95% confidence interval, reject H₀ at the 5% level of significance. The data do not indicate a difference in population mean percentage increases between company revenue and CEO salaries.

Since _d = 0 from the null hypothesis is not in the 95% confidence interval, do not reject H₀ at the 5% level of significance. The data indicate a difference in population mean percentage increases between company revenue and CEO salaries.

Since _d = 0 from the null hypothesis is in the 95% confidence interval, do not reject H₀ at the 5% level of significance. The data do not indicate a difference in population mean percentage increases between company revenue and CEO salaries.

Since _d = 0 from the null hypothesis is not in the 95% confidence interval, reject H₀ at the 5% level of significance. The data indicate a difference in population mean percentage increases between company revenue and CEO salaries.