Question 1048818
a)
For a population with unknown mean  and known standard deviation , 
a confidence interval for the population mean is: CI = x-bar ± {{{z*sigma/sqrt(n)}}}
CI =  = 60 ± {{{z*10/sqrt(22)}}} 99% confidence level: z = 2.576
CI =  = 60 ± {{{2.576*10/sqrt(22)}}}
b)
For a population with unknown mean  and unknown standard deviation , 
a confidence interval for the population mean is: CI = x-bar ± {{{t*s/sqrt(n)}}}
CI = 60 ± {{{t*10/sqrt(22)}}} 
99% confidence level, Degree of Freedom(n-1) = 21: t = 2.83 (use Caculator 0r table)
CI = 60 ± {{{2.831*10/sqrt(22)}}}