EXPERIMENTAL DESIGN VOCABULARY

EXPERIMENTAL DESIGN VOCABULARY Problem—An experiment is often based on an observation. The purpose of an experiment is often stated as a research question. Hypothesis—an educated guess about how changing the independent variable will affect the dependent variable. It’s a prediction, based on research and observations. When investigating a cause-and-effect type problem, hypotheses are written as if-and-then statements. For example: If plants are fertilized more, then they will grow taller.

A clearly written hypothesis: answers the problem is brief and to the point uses the same word pattern as the question If ___________________ is ____________________ (independent variable) (how the IV is changed) then ___________________ will __________________ (Dependent variable) (predict the effect)

Variable—characteristics in an experiment that change or could be changed Independent Variable—variables you change on purpose; also called the manipulated variable. Levels of the Independent Variable—the way(s) in which the independent variable is changed by the experimenter; these are the independent variables being tested. Dependent Variable—variable that responds to a change in the independent variable; also called the responding variable. It is what may be affected by the independent variable.

Controlled Experiment (control)—it’s a standard for comparison in an experiment. It’s the unchanged or “normal” condition in an experiment. For example: If the problem is: How does the height of a basketball hoop effect the number of points scored? Then the controlled experiment would be the 10 foot hoop because it is the “normal” height.

Constants—characteristics in an experiment that stay the same in all trials and all independent variable levels. Repeated Trials—the number of times an experiment is repeated for each level, or value, of the independent variable. The more trials, the more reliable your results.

5. Levels of the Independent Variable—the way(s) in which the independent variable is changed by the experimenter; these are the independent variables being tested.