Variable

Any factor or characteristic that can change or take on different values in a study (e.g., age, test scores, reaction time).

Hypothesis

A testable prediction about the relationship between two or more variables.

Falsifiability

The ability of a hypothesis to be disproven by evidence; a key characteristic of a scientific hypothesis

Correlational Study

A research method that examines the relationship between two variables without manipulating them. It does not establish causation.

Positive Correlation

As one variable increases, the other also increases (e.g., studying more → higher test scores).

Negative Correlation

As one variable increases, the other decreases (e.g., more stress → lower sleep quality).

No Correlation

No relationship between the two variables.

Causation

The relationship where one variable directly affects another, indicating that changes in one variable produce changes in the other.

Directionality Problem

In correlational studies, it's unclear which variable influences the other (e.g., does stress cause poor sleep, or does poor sleep cause stress?).

Third Variable Problem

A separate, unmeasured variable that influences both variables in a study, making it appear that they are related when they aren’t.

Experiment

A research method that manipulates one variable (IV) to determine its effect on another variable (DV), allowing for causal conclusions.

Quasi-Experiment

A research design that resembles an experiment but lacks random assignment to groups, often used when randomization is not feasible. Other factors (third variables) might explain the results, making it harder to prove causation.

Independent Variable (IV)

The factor manipulated by the researcher (e.g., amount of sleep). What the researcher changes or controls.

Dependent Variable (DV)

What the researcher measures to see the effect of the IV. (e.g., test scores).

Operational Definition (Operationalization)

A clear, precise definition of how a variable is measured in a study (e.g., defining "stress" as heart rate above 100 bpm).

Experimental Group

The group in an experiment that receives the treatment or intervention (IV), allowing researchers to compare results with the control group.

Control Group

The group in an experiment that does not receive the treatment or intervention (DV), serving as a baseline to compare with the experimental group.

Random Assignment

The process of randomly allocating participants to different groups in an experiment to ensure each participant has an equal chance of being assigned to any group, minimizing bias.

Between-Group

A test where two groups experiences only one condition. (Group A studies with music. Group B studies without music.)

Within-Group

A test where there is one group that experinces both conditions. (The Group studies with music, takes a test then studies without music and takes a test.)

Order Effects

When the order of which condition you experience affects the results (e.g., getting better at a task just from practice).

Counterbalancing

Used in Within-Group. Helps to prevent Order Effects. Instead of everyone doing the same order, you switch things up: Half of the students do music first, then no music.
The other half do no music first, then music.

Population

The entire group the study is trying to understand (e.g. everyone in America).

Sample

A smaller group selected from the population for the study.

Stratified Sampling

Dividing the population into subgroups and randomly selecting participants from each subgroup to ensure representation (like if 50% of america is females, then they will divide the men and woman apart and pick participants from each group).

Convenience Sampling

Using participants who are easily available, which can introduce bias.

Placebo Effect

When participants experience a change because they believe they received a treatment, even if they didn’t.

Hawthorne Effect

When participants change their behavior simply because they know they are being observed.

Placebo Method

Giving a fake treatment to a control group to test the true effects of an actual treatment.

Single-Blind Study

Participants don’t know if they are in the experimental or control group, reducing bias.

Double-Blind Study

Neither the participants nor the researchers know who is in which group, preventing experimenter bias.

Experimenter Bias

When researchers unintentionally influence results to match their expectations.

Overconfidence

The tendency to overestimate the accuracy of our own knowledge or predictions.

Confirmation Bias

The tendency to seek out or interpret information in a way that confirms our preexisting beliefs.

Social Desirability Bias

When participants respond in a way they think is more socially acceptable rather than truthfully.

Naturalistic Observation

Observing behavior in a real-world setting without interference.

Case Study

An in-depth examination of a single person or small group.

Qualitative Research

Research focused on non-numerical data (e.g., interviews, observations).

Quantitative Research

Research focused on numerical data (e.g., surveys, experiments).

Mixed-Methods Research

Combining qualitative and quantitative approaches for a more comprehensive analysis.

Structured Interview

A set of pre-planned questions asked to every participant in the same way.

Coding

Organizing qualitative data into themes or categories.

Likert Scale

A rating scale used to measure attitudes or opinions (e.g., 1 = Strongly Disagree, 5 = Strongly Agree).