Currently, I'm working on a meta-analysis that is basically based on data obtained from individual-studies. However, there are some cases where the authors report effect size value with exactly zero standard error. I understand standard error cannot be zero & the problem is related to rounding decimal places. Is there some way to handle such cases? Any help is much appreciated!
It might be possible to obtain the precise value of standard error from other reported characteristics. For example, if the effect sizes are computed as standardized measures, such as Cohen's d or correlation coefficient, the sample size and effect size are all the information needed for obtaining the standard error. See this question for obtaining the variance of Cohen's d - its square root is equal to the standard error. Or, if the effect size is a mean difference and the authors report the t-statistic or the p-value, you divide the effect size by the t-statistic and obtain the standard error (t = eff/se). Another option might be calculating it from sample sizes and standard deviations if there were reported and a non-standardized effect size measure was used.
If neither of those options is possible, I guess that you might try using a standard error estimate from a study that is the most similar in terms of sample size and methodology. Then check how the inclusion of this study with the "guessed" standard error affects the overall estimate and how sensitive the overall estimate is to different values of the "guessed" standard error.