Note: If more than $13,000 of debt is canceled in one year, the gift giver has to file a gift tax return (although they almost certainly will not owe a tax). That should not affect you as the recipient. Example: Roxy borrowed $6,000 from her dad while she was unemployed. She wrote up a promissory note for the debt.
Control Group and Experimental Group. True experiments must have a control group, which is a group of research participants that resemble the experimental group but do not receive the experimental treatment. The control group provides a reliable baseline data to which you can compare the experimental results.
Lab experiments are controlled experiments, although you can perform a controlled experiment outside of a lab setting! In a controlled experiment, you compare an experimental group with a control group. Ideally, these two groups are identical except for one variable, the independent variable.