A simple random sample of size 20 is drawn from a population

A simple random sample of size 20 is drawn from a population that is known to be normally distributed. The sample variance, s^2, is determined to be 13. Construct a 90% confidence interval for sigma^2.

Solution

Intermediate Calculations

Degrees of Freedom

19

Sum of Squares

247

Single Tail Area

0.05

Lower Chi-Square Value

10.1170

Upper Chi-Square Value

30.1435

Interval Lower Limit for Variance

8.1941

Interval Upper Limit for Variance

24.4143

90% CI=(8.19, 24.41) ( two decimals)

Intermediate Calculations
Degrees of Freedom	19
Sum of Squares	247
Single Tail Area	0.05
Lower Chi-Square Value	10.1170
Upper Chi-Square Value	30.1435
Interval Lower Limit for Variance	8.1941
Interval Upper Limit for Variance	24.4143