AP Psychology - Correlation, Experimentation & Statistical Reasoning

Vocabulary practice flashcards covering Unit 0 (Modules 0.4 & 0.6) concepts including correlation, experimental controls, descriptive statistics, and inferential statistics.

Correlation

A statistical measure that describes the direction and strength of the relationship between two variables.

Positive Correlation

A relationship in which as one variable increases, the other variable also tends to increase.

Negative Correlation

A relationship in which as one variable increases, the other variable tends to decrease.

Zero Correlation

A correlation coefficient close to $0$, indicating that no relationship exists between two variables.

Correlation Coefficient Strength

The degree of association indicated by proximity to $+1.00$ or $-1.00$, where values furthest from $0$ represent stronger relationships regardless of sign.

Correlation vs. Causation

The principle that an association between two variables does not prove that one variable causes the other.

Third Variable

An unmeasured outside factor (such as hours of sleep) that can potentially explain an observed correlation between two other variables.

Independent Variable

The variable in an experiment that is manipulated or varied by the researcher (e.g., whether participants receive caffeine).

Dependent Variable

The outcome variable in an experiment that is measured to determine the effect of the manipulated factor (e.g., memory performance).

Experimental Group

The group of participants in an experiment who receive the specific treatment or condition being tested.

Control Group

The baseline group of participants in an experiment who do not receive the experimental treatment (e.g., given an identical non-caffeinated beverage).

Random Assignment

The procedure of assigning participants to experimental and control groups by chance to minimize preexisting differences between the groups.

Confounding Variable

An unintended variable other than the independent variable (such as room noise level) that systematically affects the experimental results.

Mean

A measure of central tendency calculated by dividing the sum of all scores by the total number of scores.

Median

The physical middle value when dataset scores are arranged in numerical order; it is less sensitive to extreme outliers than the mean.

Mode

The score or score value that occurs most frequently in a given dataset.

Range

A simple measure of dispersion calculated as the numerical difference between the highest score and the lowest score in a dataset.

Outlier

An extreme numerical value in a data set that significantly drags the calculated mean up or down.

Standard Deviation

A measure of variation indicating how much scores spread out around the mean; small standard deviation means scores cluster closely, whereas large means scores are spread out.

Statistical Significance

A statistical finding (commonly defined as $p < .05$) indicating that an observed difference between groups is relatively unlikely to have occurred by chance alone.