Chapter 7 - Confidence Intervals and Sample - 7-4 Confidence Intervals for Variances and Standard Deviations - Exercises 7-4 - Page 404: 7

n = 10, df = 10-1=9, α = 1-0.90 = 0.1 To find χ2 right , α/2=0.05 From the table, χ2 right =16.919 To find χ2 left, 1-0.05=0.95 From the table, χ2 left =3.325 The Confidence Interval for a Variance: $ \frac{(n-1)s^2}{χ2 right}$ < $σ^{2}$ < $ \frac{(n-1)s^2}{ χ2 left}$ $ \frac{9*4.1^2}{21.666}$ < $σ^{2}$ < $ \frac{5*4.1^2}{3.325}$ = 5.0179 < $σ^{2}$ < 204.0049