Types of Variables and Scales of Measurement

Discrete Variable

Countable variable organized into separate categories.

Qualitative Variable

Categorical variable measured using labels or categories.

Independent Variable

Manipulated variable in an experimental study.

Nominal Scale

Categorical scale with no inherent order.

Ordinal Scale

Categorical scale with a ranked order.

Ratio Scale

Quantitative scale with an absolute zero point.

Interval Scale

Quantitative scale without a meaningful zero.

Caffeine

Independent variable affecting exam performance in study.

Observation

Data collected on different measurable characteristics.

Variable

Measurable characteristic that can vary in value.

Quantitative Variable

Numerical variable measured in numerical terms.

Continuous Variable

Variable that can take infinitely smaller values.

Dependent Variable

Measured variable to observe effects of manipulation.

Control Variable

Variable kept constant during an experiment.

Extraneous Variable

Uncontrolled variable that may affect the dependent variable.

Exam Performance

Dependent variable measured in caffeine study.

Heart Rate

Example of a quantitative variable measured numerically.

Temperature

Example of a continuous variable with fractional values.

Pets Owned

Example of a discrete variable counted in whole numbers.

Blood Types

Example of nominal data in a nominal scale.

Marathon Finish Order

Example of ordinal data indicating ranking.

Height Measurement

Example of a ratio scale with meaningful zero.

Celsius Scale

Example of an interval scale without absolute zero.

Study Hours

Extraneous variable affecting exam performance outcomes.

Stress Level

Extraneous variable potentially impacting exam results.

Descriptive statistics

a way to summarize and describe data. Descriptive statistics involve calculations such as the mean, median, mode, standard deviation, variance, and range of a set of scores.

Inferential statistics

inferences and generalizations about populations based on data gathered from samples. Inferential statistics involve calculations such as those used for hypothesis testing (z-scores, t-tests, ANOVA, and correlational analyses).

Statistics

the science of collecting, analyzing, interpreting, and presenting data.

data (singular: datum)

a collection of facts, figures, or information that can be analyzed to draw conclusions or make decisions.