Answer: 68
Step-by-step explanation:
As per given , we have
Population standard deviation : [tex]\sigma=4[/tex]
Critical value for 90% confidence interval =[tex]z_{\alpha/2}=1.645[/tex]
Margin of error : E= 0.8 milligrams
The formula to find the sample size is given by :-
[tex]n=(\dfrac{z_{\alpha/2}\ \sigma}{E})^2[/tex]
i.e. [tex]n=(\dfrac{(1.645)(4)}{0.8})^2=(8.225)^2[/tex]
[tex]=67.650625\approx68[/tex]
Hence, the limnologist must analyze 68 samples.
