Melatonin effects on sleep quality of COVID-19 patients: a protocol for systematic review and meta-analysis of randomised controlled trials with trial sequential analysis.

According to the Cochrane Handbook, the thresholds for interpreting the I 2 statistic are as follows: 0%–40%, probably not significant; 30%–60%, likely to reflect moderate heterogeneity; 50%–90%, likely to indicate significant heterogeneity; 75%–100%, representing considerable heterogeneity. 30 If the I value is below 50%, a fixed-effects model will be used; otherwise, a random-effects model will be used.

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