AP PSYCH Statistical Concepts

researcher bias

A tendency for researchers to engage in behaviors and selectively notice evidence that supports their hypotheses or expectations.

case study

Examines one individual in depth in hopes of revealing things true of us all.

correlation coefficient

A statistical index of the relationship between two things.

experiment

A research method in which an investigator manipulates one or more factors to observe their effect on some behavior or mental process.

Institutional Review Board

Group that reviews research in advance to ensure ethical considerations are met.

stratified sample

The population is divided into separate groups, called strata, and a probability sample is drawn from each group.

operational definition

A statement of the procedures used to measure or manipulate a research variable.

reliability

A measure of consistency.

validity

Refers to the extent to which any tool measures what it is intended or claims to quantify.

participant bias

A tendency for research participants to respond in a certain way because they know they are being observed.

survey method

Research technique in which information is gathered from people.

wording effect

The effect that question phrasing and order have on how people answer surveys.

random sample

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

cross-sectional study

Technique that compares individuals from different age groups at one time.

scatterplots

A graphed cluster of dots which represents the values of two variables.

illusory correlation

The idea of a relationship where none exists.

control group

The group that does not receive the treatment.

double blind procedure

An experimental procedure in which both the research participants and the research staff are ignorant to the expected outcome.

placebo

A non-active substance or condition that may be administered instead of a drug to see if the drug has an effect beyond expectations.

extraneous variable

A factor other than the independent variable that might produce an effect in the experiment.

statistics

Tools that help us see and interpret things we may otherwise miss.

range

The gap between the lowest and highest score.

skewed

A distribution with its peak well to one side.

risk

The chance that an accident might occur during a research project.

scientific method

A method of investigation involving observation and theory to test scientific hypotheses.

hindsight bias

The tendency to believe, after learning an outcome, that one would have foreseen it.

overconfidence

The tendency to think we know more than we do.

theory

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

hypothesis

A testable prediction.

replication

Repeating a research study or experiment.

observation

The simplest scientific technique.

dependent variable (DV)

The research variable that is influenced by the independent variable.

statistical significance

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

informed consent

Participants must be informed about the research and any potential risks involved.

population

The group being studied, from which samples may be drawn.

naturalistic observation

Observing and recording behavior in naturally occurring situations without trying to control the situation.

longitudinal study

Technique that studies the same group of individuals over a long period.

confirmation bias

A tendency to search for information that confirms one's preconceptions.

experimental group

The group that receives the treatment.

random assignment

Assigning participants to experimental and control groups by chance.

placebo effect

Experimental results caused by expectations alone.

independent variable (IV)

The variable that a researcher actively manipulates.

confounding variables

A variable that varies systematically with the independent variable.

central tendency

A single score that represents a whole set of numbers.

mean

The sum of all the scores divided by the number of scores.

median

The middle number in a set of numbers that are listed in order.

mode

The most frequently occurring score.

standard deviation

A measure of variability that describes an average distance of every score from the mean.

normal distribution

Describes a symmetrical, bell-shaped curve that shows the distribution of many attributes.

coercion

Making someone do something; not allowed according to ethical guidelines.

confidentiality

Researchers must not release data or information about individual participants.

debriefing

Participants must receive a full explanation of the research when their involvement is done.

Hawthorne effect

The process where human subjects change their behavior simply due to being observed.