levels of measurement, research question types, validity and reliability types

Nominal

Names or labels only, no order (e.g. gender, country)

Ordinal

Ordered categories but gaps are not equal (e.g. Likert scales, rankings)

Interval

Numbers with equal gaps but no true zero (e.g. temperature in °C, test scores)

Ratio

Numbers with equal gaps and a true zero meaning “none” (e.g. time, height, minutes, sleep hours)

Exploratory

Used when little is known and the goal is to explore or find ideas

Descriptive

Describes what is happening (who, what, where, how often)

Explanatory

Looks for relationships or causes (why or how something happens)

Evaluative

Tests whether an intervention or program works

Levels of measurement

What kind of data or numbers you have

Types of research questions

What the researcher is trying to find out

Nominal vs ordinal

Can I rank it? If no → nominal, if yes → ordinal

Interval vs ratio

Does zero mean none? If no → interval, if yes → ratio

Descriptive vs explanatory

Am I describing or explaining?

Explanatory vs evaluative

Is there an intervention being tested?

Validity

The extent to which a measure assesses what it is intended to measure

Construct validity

The degree to which a test truly measures the theoretical construct it claims to measure

Face validity

Whether a measure appears, on the surface, to measure what it claims to measure

Content validity

The extent to which a measure adequately covers all relevant aspects of the construct

Criterion validity

a test is good if it correctly predicts or matches a real-world outcome or trusted standard.

Predictive validity

The ability of a measure to predict a future outcome

Concurrent validity

a test is good if its results match another trusted test taken at the same time

Internal validity

The extent to which changes in the dependent variable are caused by the independent variable

External validity

The degree to which findings can be generalised beyond the study

Ecological validity

The extent to which findings generalise to real-world settings

Reliability

The consistency or stability of a measurement

Test–retest reliability

The consistency of a measure over time

Internal consistency

The degree to which items on a scale measure the same construct

Cronbach’s alpha

A statistic used to assess internal consistency

Inter-rater reliability

The level of agreement between different raters or observers

Intra-rater reliability

The consistency of ratings made by the same rater over time

Parallel-forms reliability

The consistency between different versions of the same test

Reliable but not valid

A measure that is consistent but does not measure what it intends to

Valid but not reliable

Not possible, as reliability is required for validity

Systematic measurement error

Error that consistently biases scores in one direction, reducing validity but not reliability