A study of the ages of motorcyclists killed in crashes involves the random selec

Question

A study of the ages of motorcyclists killed in crashes involves the random selection of 138 drivers with a mean of 38.64 years. Assuming that ?= 11.5 years, construct and interpret a 95% confidence interval estimate of the mean age of all motorcyclists killed in crashes. iew a t distribution table Click here to view page 1 of the standard normal distribution table. Click here to view page 2 of the standard normal distribution table What is the 95% confidence interval for the population mean ? HRound to two decimal places as needed.) Notice that the confidence interval limits do not include ages below 20 years. What does this mean? O A. The mean age of the population will most likely not be less than 20 years old. O B. Motorcyclists under the age of 20 never die in crashes. O C. The mean age of the population will never be less than 20 years old. O D. The mean age of the sample will most likely not be less than 20 years old

Explanation / Answer

Solution:- Given that X = 38.64 ,  ? = 11.5 , n = 138

Z(0.025) = 1.96

=> 95% confidence interval for the population mean = X +/- Z * ?/sqrt(n)

= 38.64 +/- 1.96*11.5/sqrt(138)

= 36.72 ,  40.56

= 36.72 < ? < 40.56

=> option A.The mean age of the population will most likely not be less than 20 years old.

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