题目
An analyst collects a sample of 50 P/E ratios of stocks that are representative of the market. The mean P/E of these stocks is 20 and the standard deviation is 8.5. What is the 95 percent confidence interval for the mean P/E of stocks in this market?
选项
A.17.21 to 22.79
B.17.64 to 22.36
C.18.02 to 21.98
D.18.31 to 21.69
答案
B
解析
The 95% confidence interval=μ＋/-1.96 × σ/ √n =20＋/-1.96× 8.5/√50=(17.6439，22.3561) 95%的置信区间 =μ＋/-1.96 × σ/ √n =20＋/-1.96× 8.5/√50=(17.6439，22.3561)