Question

Suppose you are working for a regional residential natural gas utility. For a sample of 90 customer visits, the staff time per reported gas leak has a mean of 206 minutes and standard deviation 32 minutes. The VP of network maintenance hypothesizes that the average staff time devoted to reported gas leaks is 216 minutes.

At a 10 percent level of significance, what is the lower bound of the interval for determining whether to accept or reject the VP's hypothesis?

Note that the correct answer will be evaluated based on the z-values in the summary table in the Teaching Materials section.

Please round your answer to the nearest tenth.

Note that the correct answer will be evaluated based on the full-precision result you would obtain using Excel.

Answer 1

I have used minitab17

• For two tailed case    vs

Steps

1. Stat
2. Basic statistics
3. 1 sample z
4. Enter the data as follows

1. 
2. Options
3. 
4. ok
5. ok

• For left tailed case vs   

Steps

1. Stat
2. Basic statistics
3. 1 sample z
4. Enter the data as follows
5. Options
6. 
7. ok
8. ok

• for Right tailed case    vs

Steps

1. Stat
2. Basic statistics
3. 1 sample z
4. Enter the data as follows  
5. options
6. 
7. ok
8. ok

MINITAB OUTPUT

The lower bound for both tailed 200.45

for one tailed the lower bound is 201.68

As the confidence interval doesnot contain the null hypothesis value 216 we would reject the null hypothesis.