Question 438329
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Hi
A market researcher wants to find a confidence interval estimate of the mean
 age of all TCC students. A study done earlier in the year found that the
 standard deviation of all TCC student ages was 14.2 years. How large a random
 sample must the researcher take in order to be 95% confident that margin of
 error is 3.2 years.

ME = 1.96[14.2/sqrt(n)]
 n = (1.96*14.2/ME)^2 = 1.96*14.2/3.2)^2 = 75.6465 
  Sample Size of 76 needed

re: 1.96
See Summary below of various critcal regions per confidence level:
	a	a/2	crtical regions	
90%	0.1	5%	z <-1.645	z >+1.645
95%	0.05	2.50%	z <-1.96	z >+1.96
98%	0.02	1%	z <-2.33	z >+2.33
99%	0.01	0.50%	z<-2.575	z >+2.575