A customer service representative was interested in comparing the average time (

Question

A customer service representative was interested in comparing the average time (in minutes) customers are placed on hold when calling Southern California Edison and Southern California Gas companies. The representative obtained two independent random samples and calculated the following summary information: So Cal Edison

Southern Cal Edison

Southern Cal Gas

Sample Size

9

12

Sample Mean

3.2 min

2.8 min

Sample Standard deviation

0.5 min

0.7 min

Assume the distributions of time a customer is on hold are approximately normal.

Using the following null and alternate hypothesis:
H0:mu1-mu2=0 vs. Ha:mu1-mu2 not equal 0
Test statistic is t=-1.455
Assume alpha = 0.1 what is the appropriate conclusion for this test?

Do not reject H0

none of these

Reject Ha

Reject H0

Southern Cal Edison

Southern Cal Gas

Sample Size

9

12

Sample Mean

3.2 min

2.8 min

Sample Standard deviation

0.5 min

0.7 min

Explanation / Answer

answer is C.

here calculate t =-1.455 and

p value for this t at alpha 0.1 and df 19(12+9-2=19) for two tailed is 0.1619 which is more than alpha

so we Rejct alternative hypothesis Ha.

answer is C.

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