. 2020 Sep 3;2020(9):CD007668. doi: 10.1002/14651858.CD007668.pub3

14. Comparison 3. Contingency management (CM) + standard maintenance (SM) versus SM alone: cocaine abstinence (skewed data).

Study	Outcome	Experimental group: CM + SM			Control group: SM			Statistic	Comments
		n	Mean	SD	n	Mean	SD
Messina 2003	Number cocaine‐negative specimens; by 16 weeks^a	15	39.4	11.4	12	9.3	11.3	P < 0.05 (Two‐way ANOVA; Tukey‐Kramer post hoc test; no further details)	Favours experimental group: CM + SM
ANOVA: analysis of variance; CM: contingency management; n: participant numbers reported as randomised to each condition; SD: standard deviation; SM: standard maintenance.

^aOutcome is mean number of cocaine‐negative specimens per participant.