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

Question

Quizplus · Accepted Answer

The lower limit of a 90% 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 the lower limit at 5% (since it's a two-tailed test) is approximately 10.117. The formula for the confidence interval is ( (n-1)s^2 / χ² upper, (n-1)s^2 / χ² lower ). Plugging in the values: (19*32)/30.144 = 20.170.

A Random Sample of Size 20 Taken from a Normally