Variance Procedures

Calculating the Confidence Interval

The Problem

Example # 9: Estimate the population variance, σ², using a confidence interval to indicate uncertainty. The data are:

101, 54, 77, 88, 85, 65, 57, 101, 74, 89, 74, 65, 91, 62, 83, 70, 49, 63, 40, 86, 91, 76, 70, 96, 82, 86, 89, 86, 49, 52, 72, 104, 75, 92

With this information, calculate the endpoints of the central 90% confidence interval.

Information given:

To summarize the above, the values of import are:

Summary statistics from the problem
\( s^2 \) =
\( n \) =
\( \alpha \) =

It may be helpful if you calculate these values yourself. Once you have, you can check your answers by hovering your mouse over the grey spaces to see if you calculated them correctly.

Your Answer

In the box below, please enter the two endpoints of the 90% confidence interval for the population variance, then click on the “Check your answer!” button. Please round your answer to the ten-thousandths place.

90% Confidence Bounds: (, )

Make sure the lower limit is less than the upper limit.

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