- The observed response percentages appear in the Observed N column. Because of its use as a weighting variable, these are the actual values of the variable First Class Mail.

- The expected response percentages appear in the Expected N column. Note that the values in this column are simply the historical percentages for bulk mail; you entered these in the Chi-Square Test dialog box.

- The differences between first class and bulk mail response percentages appear in the Residual column.

The firm hoped that first-class mail would result in quicker customer response. The first two weeks do show a difference in that direction, of four and seven percentage points, respectively. The question is whether the differences between the two distributions overall are large enough to make a difference.

On 11 degrees of freedom, the obtained chi-square statistic (12.249) is not statistically significant. This particular promotion did not result in response times that were significantly different from standard bulk mail.