Answer: (751.05, 766.95)
Step-by-step explanation:
We know that the confidence interval for population mean is given by :-
,
where =population standard deviation.
= sample mean
n= sample size
z* = Two-tailed critical z-value.
Given :
n= 42
We know that from z-table , the two-tailed critical value for 99% confidence interval : z* =2.576
Now, the 99% confidence interval around the true population mean viscosity :-
∴ A 99% confidence interval around the true population mean viscosity : (751.05, 766.95)