90-n=3n
90=4n
22.5=n
Final answer 22.5
Answer:
a) Standard error = 0.5
b) 99% Confidence interval: (19.2125,21.7875)
Step-by-step explanation:
We are given the following in the question:
Population mean = 20.50 mpg
Sample standard deviation = 3.00 mpg
Sample size , n = 36
Standard Error =

99% Confidence interval:

Putting the values, we get,


The second i think you did good