Need help please and thank you. The average time it takes 64 runners to finish a

Question

Need help please and thank you. The average time it takes 64 runners to finish a 2.2 mile race 13.0 minutes with a variance of 2 minutes. What is the best estimate for the average time it takes runners to finish this type of race? A.12.0 B. 12.2 C. 12.5 D. 12.8 E. 13.0 What are the 95% confidence limits for the average time it takes all runners to finish the 2.2 mile race? A. 12.65 to 13.35 B. 13.50 to 13.50 C. 12.71 to 13.29 D. 12.83 to 3.17 E. None of above What would happen if the variance of the time it takes to finish the race for these 64 runners fell from 2 minutes to 1 minute? A Margin of error would increase B. Alpha level would go up C. Width of confidence interval would decrease D. Sample size would increase E. None of the above

Explanation / Answer

1) Best point estimate = sample mean = 13

Option E is correct.

2) The statistical software output for this problem is:

One sample T confidence interval:
: Mean of population

95% confidence interval results:

Hence,

95% confidence interval is: 12.65 to 13.35

Option A is correct.

3) If variance will decrease, width of confidence interval will decrease.

Option C is correct.

Mean Sample Mean Std. Err. DF L. Limit U. Limit 13 0.17675 63 12.646793 13.353207

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