Table 5.

Parameters of summary estimate.

Parameter	Meaning
Mean differences[76]	Measures the difference between the mean value in 2 groups, experimental group and control group. Assesses the effectiveness of the experimental group. The change of means and final means can be combined.
Standardized mean differences[76,77]	Used when all studies evaluate the same outcome but measure it with different instruments or ways. SMDs equals to the mean difference of the outcomes divided by its standard deviation. The most common ones are Cohen d, Hedges’ g, and Glass’ delta.
Proportions[78]	Number of cases divided by the total population number.
Differences in proportions[78]	Difference between the proportion of a specific outcome between 2 groups.
Relative risk[79]	Risk of event in experimental group divided by risk of event in control group. RR > 1.00 indicates increased risk.
Odds ratios[79]	Odds of event in experimental group divided by odds of event in control group. OR > 1.00 indicates increased risk.
Hazard ratio[80]	Risk of an event or disease relative to an exposure. Ratio of the chance of an event occurring in treatment group over the chance of the event in a control group.

Abbreviations: OR = odds ratios, RR = relative risk, SMDs = standardized mean differences.