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A random sample of 20 houses selected from a city showed that the mean size of...

A random sample of 20 houses selected from a city showed that the mean size of these houses is 1850 square feet with a standard deviation of 320 square feet. Assume that the sizes of all houses in this city have an approximate normal distribution. The 95% confidence interval for the variance of all house sizes in this city is:
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Answer #1

Chi square critical values at 0.05 significance level with 19 df = 8.9065 , 32.8523

95% confidence interval for is

( n - 1) S2 / U < < ( n - 1) S2 / L

19 * 3202 / 32.8523 < < 19 * 3202 / 8.9065

59222.64 < < 218447.20

95% CI is ( 59222.64 , 218447.20 )

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