# Confidence Interval for Varaince & Standard Deviation

1. A sample of 23 European countries found that the variance of life expectancy was 7.3 years. What is the 95% confidence interval estimate for the variance of life expectancy in Europe?

A) 27.2 < Ï?2 < 118.3

B)5.6<Ï?2 <10.3

C)4.4<Ï?2 <14.6

D) 28.9 < Ï?2 < 115.0

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2. Find the 95% confidence interval for the standard deviation of the lengths of pipes if a sample of 26 pipes has a standard deviation of 10 inches.

A) 14.0 < Ï? < 16.0

B) 7.8 < Ï? < 13.8

C) 74.0 < Ï? < 126.0

D) 60.8 < Ï? < 190.5

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#### Solution Summary

The solution provides step by step method for the calculation of confidence interval for variance and standard deviation. Formula for the calculation and Interpretations of the results are also included. Interactive excel sheet is included. The user can edit the inputs and obtain the complete results for a new set of data.