Question

A random sample of 20 purchases showed the sample mean of $48.77 and the sample standard deviation s is $17.58. How large is the margin of error for a 80 % confidence interval for the mean purchases of all customers

Answer 1

$5.03

Explanation:

Given data

Sample Mean (M): $48.77

Sample Size (n): 20

Standard Deviation (σ) : $17.58

Confidence Level: 80%

we know that z*-Values for 80% Confidence Levels is 1.28

the expression for margin of error is given bellow\

MOE= z*σ/√n

We can now substitute into the expression and solve for the MOE as

MOE= 1.28*17.58/√20

MOE= 22.502/4.47

MOE= 22.502/4.47

MOE= 5.03

The margin of error for a 80 % confidence interval is $5.03