Two main types of designs used specifically in human lifespan studies are

Answer;

-Correlational; experimental

Two main types of designs used specifically in human lifespan studies are correlational and experimental.

Explanation;

-Psychological studies vary in design. In correlational studies a researcher looks for associations among naturally occurring variables, whereas in experimental studies the researcher introduces a change and then monitors its effects.

-An experiment isolates and manipulates the independent variable to observe its effect on the dependent variable, and controls the environment in order that extraneous variables may be eliminated. Experiments establish cause and effect. A correlation identifies variables and looks for a relationship between them.