刘同学2018-03-25 15:37:45

Use the following values from a student's t-distribution to establish a 95% confidence interval for the population mean given a sample size of 10, a sample mean of 6.25, and a sample standard deviation of 12. Assume that the population from which the sample is drawn is normally distributed and the population variance is not known. The 95% confidence interval is closest to a: A Lower bound of –2.33 and an upper bound of 14.83. B Lower bound of –0.71 and an upper bound of 13.21. C Lower bound of –2.20 and an upper bound of 14.70. 这题为什么选2.262这个系数？为什么选这个自由度？