At the end of 1990,1991,and 1992,the average prices of a share of stock in a portfolio were $34.83,$34.65,and $31.26 respectively.To investigate the average share price at the end of 1993,a random sample of 30 stocks was drawn and their closing prices on the last trading day of 1993 were observed with a mean of 33.583 and a standard deviation of 19.149.Estimate the average price of a share of stock in the portfolio at the end of 1993 with a 90 percent confidence interval.
A) [27.646,39.523]
B) [26.732,40.434]
C) [32.514,34.651]
D) [32.533,34.633]
E) [32.269,34.897]

Question

Quizplus · Accepted Answer

The correct answer is A because the 90% confidence interval is (33.583 - 1.645 * 19.149 / sqrt(30), 33.583 + 1.645 * 19.149 / sqrt(30)) = (27.646, 39.523).

At the End of 1990,1991,and 1992,the Average Prices of a Share