This was an epidemiological study, which type I have criticized before: http://exmormon.org/phorum/read.php?2,1980722,1980771#msg-1980771
It is extremely difficult to control for irrelevant factors in an epidemiological study. Unless you are looking for something very specific (e.g. the cause of a particular disease outbreak), the best you can do is use the outcome of the study to target furth
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