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A cross country athlete is interested in investigating what proportion of high s

ID: 3053559 • Letter: A

Question

A cross country athlete is interested in investigating what proportion of high school cross country runners improve their 1 mile run time by 30 seconds from the beginning of the season to the end of the season. The athlete randomly chooses 100 runners from across the state and categorizes their 1 mile run times as improved by 30 seconds or more or not improved. Of the 100 runners, 32 of them improved by 30 seconds or more. If you were asked to find the 99% confidence interval for the proportion of high school cross country runner who improve their 1 mile run by 30 seconds or more, what is the Standard Error used for calculating this confidence interval? (round proportions to the hundredths place and the SE value to the thousandths place)

Explanation / Answer

The statistical software output for this problem is:

One sample proportion summary confidence interval:
p : Proportion of successes
Method: Standard-Wald

99% confidence interval results:

Hence,

99% confidence interval: (0.20, 0.44)

Standard error = 0.047

Proportion Count Total Sample Prop. Std. Err. L. Limit U. Limit p 32 100 0.32 0.046647615 0.19984371 0.44015629
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