Weighting of effect sizes

Hi there,

Ive been using MetaAnalyst (very handy- i wish id known about it before!). Im just wondering what MetaAnalyst weights effect sizes by? In the column it has 'weight' but i cant find any ifnromation on what this is based on. It seems to do this for odds ratios as well. Also, in the data section, if you click on the variables (the name of the column) it puts an arrow up or down and changes the order of the data. This also seems to effect the effect sizes produced. Does doing this weight the variables? If yes then is there any way to turn this off?

Any help would be much appreciated!

Thanks!