Calculate a confidence interval for population mean assuming that each sample is form a normal population.

Calculate a confidence interval for population mean µ assuming that each sample is form a normal population.

(1) sample mean (x ̅)= 30, population standard deviation (σ)= 28,  number of sample (n) =49 , 95 % confidence level

(2) sample mean  (x ̅ ) = 10, population standard deviation (σ)= 9,  number of sample (n) =81, 99 % confidence level

Note that

Confidence level

90%

95%

99%

Zα/2

1.645

1.960

2.576