SOLVING PROBLEMS: CONTROLLING EXTRANEOUS VARIABLES

Emily’s Memory Experiment

• Emily faced challenges in her memory experiment due to changing testing conditions.

• The reading room closure led her to test subjects in the building's lobby, introducing potential confounds.

Physical Variables

Aspects of testing conditions requiring control.

Elimination

Technique to control extraneous variables by removing them from the experiment.

Constancy of Conditions

Procedure to avoid confounding by keeping treatment conditions identical, except for the manipulated independent variable.

Balancing

Technique to distribute the effects of extraneous variables equally across treatment conditions.

possible

Eliminate extraneous variables when…

possible

Keep treatment conditions as similar as…

treatment conditions.

Balance effects of variables evenly across…

treatment conditions.

Randomly assign individual subjects to…

experimental design.

Prioritize internal validity over external validity in…

internal validity.

External validity relies on first ensuring…

Social Variables:

Qualities of relationships between subjects and experimenters influencing experiment results.

Demand Characteristics:

• Aspects of the experimental situation eliciting specific behaviors.

• Cues influencing a subject’s response inadvertently.

Single-Blind Experiments

Subjects unaware of their treatment conditions to control demand characteristics.

Placebo Effect

Improvement in condition from inert treatment due to expectations or increased motivation.

Cover Story

False explanation of procedures to disguise the actual hypothesis.

Experimenter Bias

Any experimenter behavior creating confounding.

Double-Blind Experiment

Neither experimenter nor subjects know treatment conditions, controlling experimenter bias.

Personality Variables

Personal characteristics brought by an experimenter or volunteer subject to the experimental setting.

external validity.

Titles may bias samples, reducing…

generalizability.

Non-random subject selection leads to biased samples and less…

the experiment.

Be aware of practice and fatigue effects during…