Diversity effects 9
To assess the key constructs we developed measures consistent with theory and
measurement recommendations (see Ajzen & Fishbein, 1980; Fishbein, Triandis et al., 2001).
The measures correspond with ‘using marijuana nearly every month in the next 12 months’. For
sake of brevity we also use the label ‘regular marijuana use’ to refer to ‘using marijuana nearly
every month in the next 12 months’.
Outcome beliefs were assessed by asking students to indicate on 5-point scales the extent
to which they thought that regularly using marijuana would lead to 36 outcomes, such as losing
one’s athletic skills and being more creative (–2 = very unlikely, +2 = very likely). Conform
Burnkrant and Page (1988) we clustered the outcome beliefs into two conceptually consistent
scales, labeled “positive outcomes” (7 items, e.g., be like the coolest kids, have a good time;
alpha = .76) and “negative outcomes” (29 items, e.g., damage my brain, lose friends, be a bad
role model; alpha = .97, r
negative beliefs, positive beliefs
= -.31, p < .001).
Six normative beliefs were assessed on five-point scales, relating to perceived
(dis)approval of students’ regular marijuana use by their close friends, dating partner, people
their own age, parents, teachers, and grandparents (–2 = ‘strongly disapprove’, +2 = ‘strongly
approve’). Conform Burnkrant and Page (1988) the first three normative beliefs were grouped
together to form a scale of peer norms (alpha = .78), and the second three beliefs formed a scale
of authority figures’ norms (alpha = .71, r
peer norms, authority norms
= .44, p < .001).
Four seven-point semantic differential items ranging from –3 to +3 measured attitude
toward regular marijuana use. Participants were asked ‘Your using marijuana nearly every month
for the next 12 months would be:’ followed by the semantic differentials ‘bad – good’, ‘dumb –
smart’, ‘unenjoyable – enjoyable’, and ‘unpleasant – pleasant’. Scores on the four items were
averaged to yield an indicator of attitude toward regular marijuana use, alpha = .87.
Convention