Table 1.

Definition of measurement properties for PA questionnaires, adapted from the COSMIN methodology [135] (p. 743)

Domain	Measurement property	Aspect	Definition
Reliability			The degree to which the measurement is free from measurement error
	Internal consistency		The degree of the interrelatedness among the items
	Reliability		The proportion of the total variance in the measurements which is because of true differences among participants
	Measurement error		The systematic and random error of a participant’s score that is not attributed to true changes in the construct
Validity			The degree to which an instrument measures the construct it purports to measure
	Content validity		The degree to which the content of an instrument is an adequate reflection of the construct
		Face validity	The degree to which the items of an instrument indeed look as though they are an adequate reflection of the construct
	Construct validity		The degree to which the scores of an instrument are consistent with hypotheses (for example with respect to internal relationships, relationships to scores of other instruments) based on the assumption that the instrument validly measures the construct
		Structural validity	The degree to which the scores of an instrument are an adequate reflection of the dimensionality of the construct
		Hypotheses testing	Idem construct validity
		Cross-cultural validity	The degree to which the performance of the items on a translated or culturally adapted instrument are an adequate reflection of the performance of the items of the original version of the instrument
	Criterion validity		The degree to which the scores of an instrument are an adequate reflection of a gold standard
Responsiveness			The ability of an instrument to detect change over time in the construct
	Responsiveness		Idem responsiveness

COSMIN COnsensus-based Standards for the selection of health Measurement INstruments, PA physical activity