Question

Sellers in Ebay wonder if the type of photo posted with an item affects the selling price of that item. One hundred and forty three Mario Kart packages were analyzed, which were classified as having a "stock" photo or not. A 95% confidence interval for the average difference in selling price between those without and with "stock" photos (mu_no - mu_yes) is (-$7.20, -$1.14).

Which of the following are correct interpretations of this interval?

a. We have evidence that packages with stock photos sell, on average, more than packages without stock photos.

b. There is no evidence that photo type is associated with the selling price.

c. We have evidence that packages with stock photos sell, on average, less than packages without stock photos.

d. In general, the average selling price of the Mario Kart packages is less than $10. More than one statement is correct.

Answer 1

Here we given the 95% confidence interval for _no - _yes is

-7.20 < (_no - _yes) < -1.14

So from upper and lower limit we can say  _no - _yes < 0

  _no < _yes.

Interpretation of confidence interval is

We have evidence that packages with stock photos sell, on average, more than packages without stock photos