SOLUTION: 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

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Question 438329: 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.
Answer by ewatrrr(24785) About Me  (Show Source):
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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