Practical calculation of mean, pooled variance, variance, and standard deviation, in meta-analysis studies

In order to perform the data analysis process, mean value and variance  or standard deviation  are required in a meta-analysis study for integrating data. However, sometimes reports published from studies only report Median, Range and Sample size. When no indication of the distribution of primary data (normal distribution or lack of normal distribution) is available, items such as mean and variance and standard deviation can be estimated based on simple formulas . The purpose of this article is merely to introduce proven formulas with applied examples.