Mean 
Sample standard deviation 
Population standard deviation 
Sample size 
Confidence level 
Confidence interval 
100 
20 
na 
25 
95 % 

100 
20 
na 
25 
90 % 

100 
40 
na 
25 
90 % 

100 
40 
n.a. 
16 
90 % 

100 
n.a. 
40 
16 
90 % 
How does the confidence level affect the width of the confidence interval, other things equal?
How does the size of the standard deviation affect the width of the confidence interval, other things equal?
How does sample size affect the width of the confidence interval, other things equal?
How does knowing the population standard deviation affect the width of the confidence interval, other things equal?
width = critical value * sd/sqrt(n)
critical value is monotic function of confidence level
How does the confidence level affect the width of the confidence interval, other things equal?
increasing confidence level increases the width
How does the size of the standard deviation affect the width of the confidence interval, other things equal?
if standard deviation increases, width increases
How does sample size affect the width of the confidence interval, other things equal?
if sample size increases, width decrease
How does knowing the population standard deviation affect the width of the confidence interval, other things equal?
it decreases the width , as zvalue will be used instead of tcritical value
and z< t for same confidence level
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