Question

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?

Answer 1

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 z-value will be used instead of t-critical value

and z< t for same confidence level