What's Random It is easy to confuse different sources of randomization and the reasons as to why each is important to experimentation. The following table lists the likely effect when random assignment is used (or not) and random sampling is used (or not). Six entries have been left out of the table and scrambled in the list below Match the effect descriptions to their corresponding letters in the table Descriptions Letter

1. Confounding not addressed; results generalize to population

2. Experimental conclusions do not generalize to population

3. Confounding not addressed; so weak claim for causation with results

4. Confounding addressed; results generalize to population

5. Experimental conclusions generalize to population 6. Confounding addressed; results don't generalize beyond sample