Answer: A. (8.4,12.6)
Step-by-step explanation:
Confidence interval is given by :-
, where n is the sample size
= Population standard deviation.
= Sample mean
= Two tailed z-value for significance level of .
Given : Confidence level = 99% = 0.99
Significance level =
By standard normal z-value table ,
Two tailed z-value for Significance level of 0.01 :
Also,
n=100
Then, the required 99% confidence interval for the average number of chips per cookie :-
Hence, the 99% confidence interval for the average number of chips per cookie = (8.4,12.6)