A random sample of size 20 taken from a normally distributed population resulted in a sample variance of 32. The lower limit of a 90% confidence interval for the population variance would be:
A) 52.185
B) 20.375
C) 20.170
D) 54.931
E) 29.655

Question

Quizplus · Accepted Answer

The lower limit of the 90% confidence interval for the variance can be found using the chi-square distribution with degrees of freedom n-1, where n is the sample size.

The chi-square value for a 90% confidence interval and 19 degrees of freedom (20-1) is 29.707.

The lower limit of the confidence interval is then (n-1)*s^2/chi-square value = (19*32)/29.707 = 20.170.

Therefore, the answer is C, 20.170.

A Random Sample of Size 20 Taken from a Normally