Question

At a recent meeting, the manager of a national call center for a major Internet bank made the statement that the average past-due amount for customers who have been called previously about their bills is now no larger than $20. Other bank managers at the meeting suggested that this statement may be in error and it needs to be tested. The file called Bank Call Center attached below, contains data for a random sample of 67 customers from the call center population. What should be conducted based on the sample data? Test using α = 0.10

Answer 1

As the calculated z does not fall in the critical region we fail to reject H0 and conclude that there is sufficient evidence that the average past-due amount for customers who have been called previously about their bills is now no larger than $23.

Explanation:

As the standard deviation for the past due amounts is 63

The sample size n= 67

1) Formulate the null and alternate hypothesis

H0: u ≤ 23 against the claim Ha: u > 23

2) The test statistics is

Z= x- u / σ/ √n

z= 20- 23/ 63/ √67

z= 0.00581

z= 0.006

3) The significance level ∝= 0.1

4) The critical value for ∝= 0.1 is Z > ±2.33

5) As the calculated z does not fall in the critical region we fail to reject H0 and conclude that there is sufficient evidence that the average past-due amount for customers who have been called previously about their bills is now no larger than $23.