Table 2 Paired two-tailed t-test, effect size (Cohen’s d) and scale reliability (Cronbach’s α) post-intervention and follow-up

DVA Myth Acceptance (1 = strongly disagree, 7 = strongly agree)

2.09 (1.95–2.23) [0.56]

1.97 (1.81–2.13) [0.67]

1.50 (1.38–1.61) [0.71]

−0.48 (− 0.28–0.67)

1.45 (1.28–1.63) [0.78]

Bystander Efficacy (0–100%)

79.88 (76.51–83.26) [0.83]

81.07 (77.59–84.55) [0.87]

91.37 (89.14–93.59) [0.85]

10.30 (6.21–14.38) [0.86]

93.65 (91.29–96.00) [0.77]

Behavioural Intent (1 = not at all likely, 5 = very likely)

3.97 (3.84–4.11) [0.71]

4.03 (3.89–4.17) [0.86]

4.42 (4.32–4.52) [0.81]

0.40 (0.23–0.57)

4.44 (4.35–4.52) [0.58]

Perception of Peers’ DVA Myth Acceptance (% who would agree with statement)

35.39^b (31.20–39.57) [0.61]

34.54^c (30.11–38.97) [0.66]

23.65 (19.13–28.16) [0.75]

- 10.89 (4.63–17.16)

28.30 (26.52–35.47) [0.30]

Perception of Peers’ Behavioural Intent (1 = not at all likely, 5 = very likely)

3.68 (3.52–3.84) [0.78]

3.66 (3.49–3.83) [0.80]

4.02 (3.86–4.18) [0.87]

0.36 (0.13–0.60)

4.19 (3.96–4.42) [0.89]

Bystander Behaviours (1 took action, 0 not in situation, −1 didn’t take action)

0.74

(− 0.39–1.87) [0.74]

0.88^d (− 0.35–22) [0.69]

1.41^d (0.23–2.80) [0.79]

0.53

(−1.31–2.37)

2.16^e (0.57–3.76) [0.71]

Number of listed bystander scenarios experienced (i.e. scored either 1 or − 1)

8.24 (7.04–9.43)

7.92^d (6.56–9.28)

7.94^d (6.76–8.82)

0.02 (− 1.76–1.80)

8.89^e (6.14–8.94)

Perceived Law Knowledge (1 = very poor, 5 = very good)

2.75 (2.50–3.00)

2.79 (2.52–3.06)

3.67 (3.48–3.87)

0.89 (0.66–1.11)

3.92 (3.70–4.14)