Question

In: Statistics and Probability

1. Suppose a sample of 30 students take an IQ test. If the sample has a...

1. Suppose a sample of 30 students take an IQ test. If the sample has a standard deviation of 12.23, find a 90% confidence

interval for the population standard deviation.

Expert Solution

Solution :

Given that,

s = 12.23

s2 = 149.5729

n = 30

Degrees of freedom = df = n - 1 = 30-1 = 29

At 90% confidence level the 2 value is ,

= 1 - 90% = 1 - 0.90 = 0.10

/ 2 = 0.10 / 2 = 0.05

1 - / 2 = 1 - 0.05 =0.95

2L = 2/2,df = 42.557

2R = 21 - /2,df = 17.7084

The 95% confidence interval for is,

(n - 1)s2 / 2/2 < < (n - 1)s2 / 21 - /2

(29)149.5729 /42.557 < < (29)149.5729/17.7084

10.0958< < 15.6508

( 10.0958 , 15.6508 )

orchestra answered 2 years ago

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