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Nathan D.

asked • 10/15/20

Let X = the average of the 49 races.

Suppose that a category of world class runners are known to run a marathon (26 miles) in an average of 144 minutes with a standard deviation of 13 minutes. Consider 49 of the races.


Let X

 = the average of the 49 races.


Part (a)

Give the distribution of X. (Round your standard deviation to two decimal places.)

  1. Xbar  ~ _____ (_____, _____) 

  ,  

Part (b)

Find the probability that the average of the sample will be between 143 and 147 minutes in these 49 marathons. (Round your answer to four decimal places.)_____

Part (c)

Find the 70th percentile for the average of these 49 marathons. (Round your answer to two decimal places.)

  1. _____ min

Part (d)

Find the median of the average running times.

  1. _____ min


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