Unit 0: Research Methods (AP Psych)

Hindsight Bias

The tendency to believe, after learning an outcome, that one would have foreseen it; also known as the “I-knew-it-all-along” phenomenon.

Theory

An explanation using an integrated set of principles that organizes observations and predicts behaviors or events.

Hypothesis

A testable prediction, often implied by a theory.

Operational Definition

A carefully worded statement of the exact procedures used in a research study.

Replication

Repeating the essence of a research study to see whether the basic finding can be reproduced.

Case Study

A descriptive technique in which one individual or group is studied in depth to reveal universal principles.

Naturalistic Observation

Observing and recording behavior in naturally occurring situations without manipulation.

Survey

A descriptive technique for obtaining self-reported attitudes or behaviors of a group, usually by questioning a representative sample.

Sampling Bias

A flawed sampling process that produces an unrepresentative sample.

Population

All those in a group being studied, from which samples may be drawn.

Random Sample

A sample that fairly represents a population because each member has an equal chance of inclusion.

Correlation

A measure of the extent to which two factors vary together, indicating how well either factor predicts the other.

Correlation Coefficient

A statistical index of the relationship between two things, ranging from -1.00 to +1.00.

Variables

Anything that can vary and is feasible and ethical to measure.

Scatterplots

A graphed cluster of dots representing the values of two variables, indicating the direction and strength of their relationship.

Illusory Correlation

Perceiving a relationship where none exists or perceiving a stronger-than-actual relationship.

Regression Toward the Mean

The tendency for extreme scores or events to fall back toward the average.

Experiment

A research method in which an investigator manipulates one or more factors to observe the effect on behavior or mental processes.

Experimental Group

The group exposed to the treatment or one version of the independent variable.

Control Group

The group not exposed to the treatment, serving as a comparison for evaluating the effect of the treatment.

Randomly Assign

Assigning participants to experimental and control groups by chance to minimize pre-existing differences.

Double-Blind Procedure

An experimental procedure where both participants and research staff are unaware of who has received the treatment or a placebo.

Placebo Effect

Experimental results caused by expectations alone; any effect on behavior caused by the administration of an inert substance.

Independent Variable

The factor that is manipulated in an experiment; the variable whose effect is being studied.

Confounding Variables

A factor other than the factor being studied that might influence a study’s results.

Dependent Variable

The outcome that is measured in an experiment; the variable that may change when the independent variable is manipulated.

Validity

The extent to which a test or experiment measures or predicts what it is supposed to.

Informed Consent

Providing potential participants with enough information about a study to enable them to choose whether to participate.

Debrief

The post-experimental explanation of a study, including its purpose and any deceptions, to its participants.

Descriptive Statistics

Numerical data used to measure and describe characteristics of groups, including measures of central tendency and variation.

Histogram

A bar graph depicting a frequency distribution.

Mode

The most frequently occurring score(s) in a distribution.

Mean

The arithmetic average of a distribution, obtained by adding the scores and dividing by the number of scores.

Median

The middle score in a distribution; half the scores are above it and half are below it.

Skewed Distribution

A representation of scores that lack symmetry around their average value.

Range

The difference between the highest and lowest scores in a distribution.

Standard Deviation

A computed measure of how much scores vary around the mean score.

Normal Curve

A symmetrical, bell-shaped curve that describes the distribution of many types of data.

Inferential Statistics

Numerical data that allow one to generalize from sample data the probability of something being true of a population.

Statistical Significance

A statistical statement of how likely it is that an obtained result occurred by chance.