Table 3.

Subgroup analysis of categorical variables.

Sub-group	N	K	SMD	95% CI		P	Sig.	τ 2	I 2	Beta
Cognitive category
Executive function	9	19	0.34	0.15	0.53	<0.01	Yes	0.02	0	ns
Psychomotor speed	6	9	0.5	0.24	0.75	<0.01	Yes	0.07	33	ns
Attention	6	8	0.55	0.26	0.83	<0.01	Yes	0	0	ref
Data type
Completion time	12	21	0.55	0.38	0.72	<0.01	Yes	0.01	3	ns
Accuracy	11	16	0.21	0.002	0.42	<0.05	Yes	0	0	ref
Population
Athletes	8	20	0.47	0.29	0.65	<0.01	Yes	0.05	24	ref
general	5	15	0.41	0.21	0.62	<0.01	Yes	0	0	ns
Administration route
Capsule	10	28	0.46	0.30	0.62	<0.01	Yes	0	0	ns
Liquid	3	7	0.49	0.21	0.76	<0.01	Yes	0.05	21	ref
Gender
Male	8	17	0.33	0.14	0.51	<0.01	Yes	0.04	22	ns
Female	3	13	0.47	0.19	0.76	<0.01	Yes	0.04	10	ns
Unclear	3	7	0.54	0.28	0.79	<0.01	Yes	0	0	ref

N, number of studies; K, number of effect sizes; SMD, standardized mean difference; 95% CI, lower and upper confidence intervals; P, significance value; τ2, measure of variation around average; I2, measure of proportion of observed variance (%); Beta, regression coefficients for between-subgroup comparisons; ref, reference category; ns, no significant difference compared to reference category.