Answer: (0.00306,0.00334)
Step-by-step explanation:
Given : Sample size : n= 420000
The number of users developed cancer of the brain or nervous system =134
Then , the proportion of users developed cancer of the brain or nervous system :
Significance level :
Critical value :
The confidence interval for population proportion is given by :-
Hence, the 90% confidence interval estimate of the percentage of cell phone users who develop cancer of the brain or nervous system is (0.00306,0.00334).