“…In these cases, if the subgroup can be regarded as an independent experimental group, the set of data yielded by the subgroup was included for calculating overall effect size. For example, even though Van den Heuvel‐Panhuizen, Kolovou, and Robitzsch () divided their experimental group into three subgroups by the participants' grade levels (i.e., fourth, fifth, and sixth grade), all participants played the same game, Hit the Target, as a treatment of the research experiment. Therefore, we regarded each subgroup as an independent experimental group, the data set from each group was treated as an independent value, the effect size of each subgroup was obtained respectively for calculating overall weighted effect size .…”