Question

(Using Excel)

A producer of computer aided design software has received numerous calls for technical support. The company has a service standard of 4 days for the mean resolution time for questions. The manager of the technical support group has been receiving some complaints about the resolution being too long.   During one week a sample of 40 customer calls result in a sample mean of 5.25 days and a standard deviation of 13.5 days.

1. Set up the hypothesis test?   

2.  What is the alpha?

3.  What is the Standard Error of the mean

4.  Degrees of Freedom?

5.  t Test statistics?

6. What is the Critical Value?

7.  What is the p-value?

8. What is the result of your hypothesis test?

9.  Does this data prove that the time is more than 4 days?

Answer 1

1. Here claim is that mean is greater than 4

So hypothesis here is

2. As Alpha is not given we will take it

3.

4. Degree of freedom is n-1=39

5. Test statistics is

6. The t-critical value for a right-tailed test, for a significance level of α=0.05 is

tc​=1.685

Graphically

7. P value is TDIST(0.59,49,1)=0.2790

8.As test statistics is not in the rejection region and also P value is greater than alpha, we fail to reject the null hypothesis

9. We do not have sufficient evidence to support the claim that the time is more than 4 days