单选题

An analyst wants to estimate the return on the S&P 500 Index for the current year using the following data and assumptions:
·Sample size = 50 stocks from the index.
·Mean return for those stocks in the sample for the previous year = 0.114. 
·Variance = 0.0529.
·The reliability factor for a 95% confidence interval with unknown population variance and sample size greater than 30 is z.025 = 1.96.
If he assumes that the S&P 500 return this year will be the same as it was last year, which of the following is the best estimate of the 95% confidence interval for this year's S&P 500 return?

【正确答案】 B
【答案解析】

The reliability factor for a 95% confidence interval with unknown population variance and sample size greater than 30 isz.025 = 1.96.The confidence interval estimate is:
With sample variance of 0.0529, s =
The estimated interval is: 0.114 ± 1.96 ×