Professor Middlebrain notes that rats in the first 10 cages, which were injected with salt water, are calm. Rats in the last 10 cages, which were injected with distilled water, are aggressive. He concludes that salt decreases aggressiveness. What is wrong with this study?

A) lack of random assignment
B) lack of an independent variable
C) lack of a dependent variable
D) presence of demand characteristics

Random Assignment

A method used in experiments to place participants into groups in a way that each has an equal chance of being assigned to any group, minimizing biases.

Independent Variable

The variable in an experiment that is manipulated by the researcher to observe its effect on the dependent variable.

Dependent Variable

In experimental and statistical research, the variable that is being tested and measured, and is expected to change as a result of manipulations to the independent variable.