A customer wants to estimate the average delivery time of a

A customer wants to estimate the average delivery time of a pizza from the local pizza parlor. Over the course of a few months, the customer orders 27 pizzas and records the delivery times. The average delivery time is 21.06 with a standard deviation of 8.442. If the customer estimates the time using a 90% confidence interval, what is the margin of error?

A. 0.7303

B. 2.7711

C. 2.1364

D. 1.6247

E. 2.7673

Solution

Margin of Error = t a/2 * (sd/ Sqrt(n))
Where,
x = Mean
sd = Standard Deviation
a = 1 - (Confidence Level/100)
ta/2 = t-table value
Mean(x)=21.06
Standard deviation( sd )=8.442
Sample Size(n)=27
Margin of Error = t a/2 * 8.442/ Sqrt ( 27)
= 1.706 * (1.625)
= 2.7711