A measure of the consistency of observations of a single situation made by different people refers to:

Inter-rater reliability measures the consistency of observations of one situation made by different people.

It shows how far independent raters agree when scoring the same event.

Construct validity concerns whether a measure reflects the intended theoretical concept.

Internal validity concerns confidence in causal inference within a study.

Split-half reliability checks internal consistency by correlating two halves of one test.

Inter-rater agreement is often quantified with Cohen's kappa.