A sample of 21 elements is selected to estimate a 90% confidence interval for the variance of the population. The chi-square value(s) to be used for this interval estimation is (are)
A)-1.96 and 1.96
B)12.443
C)10.851 and 31.410
D)12.443 and 28.412

Question

Quizplus · Accepted Answer

For a sample size of 21, the degrees of freedom is 20. The chi-square values for a 90% confidence interval with 20 degrees of freedom are approximately 10.851 (lower) and 31.410 (upper).

A Sample of 21 Elements Is Selected to Estimate a 90