In the Sommers and Ellsworth (2001) experiment on the effects of race on a trial verdict, explain how the interaction provided important information. Were the independent variables qualitative or quantitative? the dependent variables?

What will be an ideal response?

In the Sommers and Ellison experiment, there was no difference in sentencing for black defendants when a mock trial involved a specific statement about racial issues. On the other hand, when race was not mentioned, black defendants received longer sentences than white defendants. If there had been only one variable, the investigators would not have seen the complex pattern of results.
That is, if the researchers had only compared sentences of black and white defendants in race-salient trials, they would have concluded that race was unimportant on sentence length. If the researchers had only compared sentences of black and white defendants in non-race-salient trials, they would have concluded that race did make a difference. The truth is more complex: race sometimes makes a difference, but sometimes it doesn't. You need a factorial design to see this complexity.