In: Statistics and Probability
Banking fees have received much attention during the recent economic recession as banks look for ways to recover from the crisis. A sample of 41 customers paid an average fee of $11.95 per month on their interest-bearing checking accounts. Assume the population standard deviation is $1.67. Complete parts a and b below.
a. Construct a 99% confidence interval to estimate the average fee for the population.
The 99% confidence interval has a lower limit of and an upper limit of . (Round to the nearest cent as needed.)
b. What is the margin of error for this interval
ANSWER:
Given that,
Banking fees have received much attention during the recent economic recession as banks look for ways to recover from the crisis. A sample of 41 customers paid an average fee of $11.95 per month on their interest-bearing checking accounts. Assume the population standard deviation is $1.67. Complete parts a and b below.
Sample size = n = 41
Mean = = 11.95
Population standard deviation = = 1.67
a. Construct a 99% confidence interval to estimate the average fee for the population.
The 99% confidence interval has a lower limit of and an upper limit of . (Round to the nearest cent as needed.)
c = 99% =99/100 =0.99
= 1-c = 1-0.99 = 0.01
/2 = 0.01/2 = 0.005
Critical value = Z/2 = Z0.005 = 2.58
99% CI = Z/2 * (/sqrt(n))
99% CI = 11.95 2.58 * (1.67/sqrt(41))
99% CI = 11.95 0.67289027
99% CI = 11.95 - 0.67289027 , 11.95 +0.67289027
99% CI = 11.27710973 , 12.62289027
99% CI = 11.28 to 12.62
b. What is the margin of error for this interval
Margin of error = Z/2 * (/sqrt(n))
Margin of error =2.58 * (1.67/sqrt(41))
Margin of error = 0.67289027
Margin of error = 0.67289
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