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.

Question

Quizplus · Accepted Answer

The lower limit of the confidence interval for the population variance is calculated using the chi-square distribution. For a sample size of 20, the degrees of freedom is 19. Using the chi-square table, the critical value for 90% confidence interval at the lower tail is approximately 10.117. The formula for the lower limit is (n-1)s^2/χ²(α/2), which gives (19*32)/10.117 = 20.170.

A Random Sample of Size 20 Taken from a Normally