A biologist has found the average weight of 12 randomly sele

A biologist has found the average weight of 12 randomly selected mud turtles to be 8.7 lbs with standard deviation 3.6 lbs. Find a 90% confidence interval for the population mean for all such turtles.

Solution

Given a=0.1, |t(0.05,df=n-1=11)|=1.8 (check student t table)

So 90% CI is
xbar±t*s/n

--> 8.7±1.8*3.6/sqrt(12)

--> (6.829385, 10.57061)