Question

9. The following sample of lengths was taken from 9 rods off the assembly line. Construct the 99% confidence interval for the population standard deviation for all rods that come off the assembly line. Round your answers to two decimal places. 18.9,18.9,19.0,18.7,18.8,19.0,19.4,18.6,18.6

Answer 1

9)

Solution :

Given that,

s² = 0.06

n = 9

Degrees of freedom = df = n - 1 = 8

At 99% confidence level the ² value is ,

²_L = ²_/2,df = 21.955

²_R = ²_{1 - /2,df} = 1.344

The 95% confidence interval for is,

(n - 1)s² / ²_/2 < < (n - 1)s² / ²_{1 - /2}

  8 * 0.06 / 21.955 < < 8 * 0.06 / 1.344

0.15 < < 0.60

( 0.15 , 0.60)