Hi, I am conducting a systematic review and meta-analysis. I encounter an issue, which is not all included studies reported with mean +/- SD. Some reported with a mean (IQR 1-3). However, I can circumvent this problem using a formula derived from this study by Wan et al. from BMC Medical Research Methodology. My question though, can someone explain the meaning of this verbatim " where Φ−1(z) is the inverse function of (z), or equivalently, the upper zth percentile of the standard normal distribution". What is the upper zth percentile? Thanks in advance.