The eBay power seller in the previous question upon analyzin

The eBay power seller in the previous question, upon analyzing the results, finds that the mean approval score of the customers who received free shipping is 88.5 with a standard deviation of 11.4.

What is the highest confidence level for which you can claim that offering free shipping results in an improved customer approval score?

Enter your answer as a percentage, rounded to the nearest percent. For example, 0.535 would be 54%.

How do I find this number? I want to know HOW to do it.

Solution

mu = 83.4

sample mean x bar = 88.5

s = 11.4

n =14

Std error = 11/4/rtn = 3.047

H0: mu = 83.4

Ha: mu>83.4

(one tailed test)

Mean diff=88.5-83.4 = +5.1

t statistic = 5.1/3.047

=1.673

df = 13

The P-Value is .059103.

Since p value is 0.059103

we conclude that upto highest 94% level improved