If this is a question your asking yourself- weigh the specificity of your qualifying criteria against the importance of recruiting live. If live recruiting is very important, it may be best to place the screener code on the busy page and tailor your screening questions to identify qualified users. (Just between you and us, we find we get the most interesting feedback with live recruiting.) Of course, the code can reside on as many pages as you like, so the answer could also be “both”.
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