control subjects
when one designs a scientific experiment, it's important to have a control group. the subject group and the control group should be matched. like same socio-economic mix. same ethnic mix. etc. details depend on what you're studying. it's also important that the control group and the subject group be independent. like students at different schools. they certainly shouldn't be related. and the two groups shouldn't be competing against each other. otherwise your results are garbage. sheehs. how hard is this?