Experimental Design Vocab

AP Psyc

Independent Variable (IV)

The variable that the researcher deliberately changes or manipulates in an experiment to test its effects. It is the presumed cause in a cause-and-effect relationship

Dependent Variable (DV)

The variable that is observed and measured to see if it changes in response to the independent variable. It represents the outcome or data being collected.

Confounding Variable

An unmeasured or uncontrolled outside variable that influences both the independent and dependent variables. It can distort the results, making it difficult to determine the true cause-and-effect

Operational Definition

specifies how a researcher will measure and manipulate variables in a studyand outlines the procedures used to ensure consistency and reliability in the measurement process.

Experimental Group

The group of participants in an experiment who are exposed to the independent variable or treatment being tested.

Control Group

The group of participants who are not exposed to the independent variable or active treatment. They provide a baseline comparison to see if the independent variable actually caused a change.

Random Assignment

A method of placing participants into different experimental conditions purely by chance. This ensures that every participant has an equal likelihood of being in any group, which helps equalize individual differences across groups.

Placebo Effect

A phenomenon where participants experience actual physical or psychological changes simply because they believe they are receiving a treatment, even if the treatment is inactive or fake.

Experimenter Bias

When a researcher's expectations, beliefs, or preferences subtly and unintentionally influence how they conduct the study, interact with participants, or interpret the data.

Single Blind Study

A research design where the participants do not know whether they are in the experimental or control group, but the researchers do. This prevents participant expectations from influencing the results.

Double Blind Study

A research design where neither the participants nor the researchers interacting with them know who is in the experimental or control group. This controls for both the placebo effect and experimenter bias.

Representative Sample

A group of participants chosen from a population that accurately reflects the key demographics, traits, and diversity of the larger population, allowing findings to be generalized.

Random Sample

A technique for selecting participants from a larger population where every individual has an equal chance of being chosen. This reduces selection bias and helps ensure the sample reflects the broader population.