Basics to Research Methods 9

Nominal Variables

Variable standing for categories. You can’t rank them.

Ordinal Variable

Values can be ranked, it shows some kind of an order.

Dichotomous binomial variable

Contains two distinct vales (s3x at birth)

Multinomial variable

Contains three or more categories

Interval Variable

Has an invented zero (0°C doesn't mean "no temperature").

Ratio

Has a real, meaningful zero (0 means total absence, like 0kg weight).

Relative order / Stevens’ Measurement Theory

Values must be set in an increasing/decreasing order,

Equal Interval / Stevens’ Measurement Theory

The step/difference between any two values must be the same.

Zero Point

Whether the scale has a true zero or an arbitrary one.

Psychometry

The technology/science of test creation and construction for the quantification of psychological constructs.

Q-Sorting

A research technique where people rank-order opinion statements along a forced, quasi-normal distribution (e.g., sorting cards from "most agree" to "most disagree").

Clinical Cut-Off

A specific score used to classify individuals as likely having a condition (e.g., disorder vs. healthy). It serves as a dividing line for diagnostic decisions.

Coverage of the Construct (Content Validity)

Scale must cover multiple/different parts of the construct, not just one aspect.

Unidimensional Scale

A scale where all items correlate strongly with each other because they result from a single underlying dimension (like a thermometer measuring only temperature).

Multidimensional Scale

A scale with two or more underlying dimensions. Items form distinct "clusters" that correlate with each other (e.g., a Math cluster and a History cluster within a "School Performance" scale).