A study of the ages of motorcyclists killed in crashes invol

A study of the ages of motorcyclists killed in crashes involves the random selection of 160 drivers with a mean of 34.69 years. Assuming that =11.4 years, construct and interpret a 90% confidence interval estimate of the mean age of all motorcyclists killed in crashes.

What is the 90% confidence interval for the population mean ?

Solution

90% confidence interval = [ mean - ( t-score * / sqrt (n) , mean + ( t-score* / sqrt (n) ] .....
t-score for 90% confidence and df 159 = 1.654494..

lower limit = 34.69 - ( 1.654494 * 11.4 / sqrt(160) ) = 33.19889 ......
upper limit =  34.69 - ( 1.654494 * 11.4 / sqrt(160) ) = 36.18111 .....

90% confidence interval = [ 33.19889 , 36.18111 ].....

90% confidence level means that we would expect 90% of this interval estimates to include the population parameter i.e the   population mean ....