Number of papers which used statistical methods reported the method used and also used an error measure.

†Statistical methods described in materials and methods section of paper. ‡Standard error of the mean, confidence interval, standard deviation or other error measurement. *70% (174/247); 91% (247/271) of all included studies used statistical methods to analyse the data; 17% (46/267) of the studies, that presented numerical data, did not present a measure of variation (e.g. standard deviation) or uncertainty (e.g. standard error of the mean [SEM] or confidence interval [CI]).