Variable – Anything that can have different values or change.
Testable hypothesis – A prediction that can be tested to see if it is supported or proven wrong by observations.
Operational definition – A clear explanation of exactly how a variable will be measured or tested.
Dependent variable – The variable that is measured or recorded during an experiment.
Independent variable – The variable that the researcher changes or controls in an experiment.
Population – The entire group of people or things that a researcher wants to learn about.
Sample – A smaller group chosen from the population to be studied.
Random sampling – A method where every member of the population has an equal chance of being chosen for the study.
Case study – A detailed study of one person.
External validity – How well the results of a study apply to real life and other people or situations.
Demand characteristics – Clues that tell participants what the researcher expects or wants them to do.
Double-blind design – A study where neither the participants nor the researchers know who is in each group.
Correlation – A relationship between two variables that change together. If one increases and the other increases, it is a positive correlation. If one increases while the other decreases, it is a negative correlation.
Validity – How well a test or method measures what it is supposed to measure.
Quasi-experiment – A study that compares groups that already existed instead of groups created by the researcher.
Correlational studies – Studies that look at how variables are related without changing or controlling those variables.
Experiment – A study where the researcher changes one variable to see if it causes a change in another variable.
Experimental manipulation – When a researcher purposely changes the independent variable to see what happens.
Experimental group – The group that receives or experiences the change made by the researcher.
Control group – The group that does not receive the experimental change. It is used for comparison.
Random assignment – Randomly placing participants into different groups so the groups are similar at the beginning of the experiment.
Internal validity – How sure we can be that the independent variable caused the change in the dependent variable.
Replication – Repeating a study or experiment to see if you get the same results.
Informed consent – When a person agrees to participate in a study after being told what the study will involve.
Debriefing – When the researcher explains the purpose and details of the study to participants after the experiment is finished.
IRB (Institutional Review Board) – A group that reviews research involving people to make sure their rights, safety, and well-being are protected.
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