Table 3.

Results of meta-regression analysis.

Variables	Number of studies	P-Value	Tau2	I2 (%)	Adj R2 (%)
Gender	20	0.992	0.8841	97.10	−5.98
Average age	8	0.952	0.0273	98.60	−17.06
Region	9	0.020	0.0031	95.27	51.15
Education	12	0.314	0.8392	98.43	1.06
Grade	15	0.272	0.0356	95.62	1.98
University type	14	0.532	0.0171	98.19	−4.98
Publication year	14	0.053	0.0127	97.32	22.35
Measurements	14	0.461	0.0169	98.17	−3.62
Sample size	14	0.822	0.0176	98.13	−8.28
Latitude	9	0.003	0.0017	93.56	73.49
GDP (2019)	7	0.253	0.0072	95.38	10.53
GDP per capita (2019)	7	0.037	0.0035	93.64	56.07

GDP, Gross Domestic Product.