TABLE 3.

Cronbach’s alpha and intra-class correlation coefficient of the Drug Attitude Inventory.

Cronbach’s alpha	Cronbach’s alpha based on standardised items	N of items	Intra-class correlation coefficient †	95% Confidence interval		F test with true Value 0
				Lower bound	Upper bound	Value	df 1	df 2	p
Reliability statistics
0.56	0.58	10	-	-	-	-	-	-	-
Intra-class correlation coefficient
Single measures	-	-	0.11‡	0.077	0.146	2.286	219	1971	< 0.01
Average Measures	-	-	0.55§	0.454	0.630	2.286	219	1971	< 0.01

A two-way mixed-effects model where people effects are random and measures effects are fixed.

^†, Type A intra-class correlation coefficients using an absolute agreement definition.

^‡, The estimator is the same, whether the interaction effect is present or not.

^§, This estimate is computed assuming that the interaction effect is absent because it is not estimable otherwise.