The table reflects the results of a study by Roediger and Karpicke (2006). The authors investigated whether the test-enhanced learning effect (the demonstration that repeated testing improves memory for material) was due merely to repeated exposure to the material. They randomly assigned participants to one of the two study conditions (study-study or study-test) and to one of three retention interval conditions (final test at a delay of 5 minutes, 2 days, or 1 week). The dependent variable was the proportion of idea units recalled from an encyclopedia passage.

5 Minutes 2 Days 1 Week Mean

Study-Study 0.80 0.55 0.42 0.59

Study-Test 0.75 0.70 0.55 0.67

Mean 0.78 0.63 0.49

Table: Test-Enhanced Learning

The cells of this study reflect a main effect of study condition.

What BEST describes that main effect?

a. On average, people in the study-test condition had better memory than people in the study-study condition.

b. On average, people in the study-study condition had better memory than people in the study-test condition.

c. On average, memory performance decreased as the retention interval increased.

d. Those in the study-test condition performed more poorly of the 5-minute recall test than did those in the study-study condition, but at longer retention intervals (2 days and 1 week); those in the study-test condition performed better than those in the study-study condition.