Question
The mean and standard deviation of a random sample of n measurements are equal to 34.1...
The mean and standard deviation of a random sample of n measurements are equal to 34.1 and 3.6, respectively.
a. Find a 90% confidence interval for μ if n=144.
b. Find a 90% confidence interval for μ if n=576.
c. Find the widths of the confidence intervals found in parts a and b. What is the effect on the width of a confidence interval of quadrupling the sample size while holding the confidence coefficient fixed?
Homework Answers
Answer #1
Part a)
Confidence Interval
Lower Limit = 
Lower Limit = 33.6033
Upper Limit = 
Upper Limit = 34.5967
90% Confidence interval is ( 33.6033 , 34.5967 )
Width of CI = 34.5967 - 33.6033 = 0.9933
Confidence Interval
Lower Limit = 
Lower Limit = 33.8529
Upper Limit = 
Upper Limit = 34.3471
90% Confidence interval is ( 33.8529 , 34.3471 )
Width of CI = 34.3471 - 33.8529 = 0.4943
Part c)
As sample size increase, width of confidence interval become narrow.
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