刘同学2018-05-21 16:26:47

A sample of 100 observations drawn from a normally distributed population has a sample mean of 12 and a sample standard deviation of 4. Using the extract from the z-distribution given below, find the 95% confidence interval for the population mean. The 95% confidence interval is closest to: A 7.840 to 27.683 B 11.216 to 12.784 C 11.340 to 12.660 什么时候用12+1.96*4，什么时候用12+1.96*4/100根号下呢？