Why we constrain the stderr to be 1 in level 1?

[dorishuntt]

Hi, every one, I need your help, please give me your suggestion.

In my data, I colletced 10 studies, all about the psychological stress level of the same category subjects (no control group), but were conducted at different time, area. The Y variable is a normal continuous variable. Data structure showed below.

Study NO. sample size Mean of score Standard deviation of score
1 60 1.88 0.56
2 46 1.44 0.47
3 89 2.01 0.65
......

My objective is to get a stable estimation of score (mean and SD) of this kind of people through multi-level meta-analysis.

Thanks.