On the Wikipedia page for data analysis, the following claim is made. "...one should not follow up an exploratory analysis with a confirmatory analysis in the same dataset. An exploratory analysis is used to find ideas for a theory, but not to test that theory as well." This claim is referenced to an obscure article, hidden behind a paywall with very little web presence to verify its existence. If this was an important condition with data analysis, one would expect a more fundamental reference, even multiple references, to support this claim.
So, I'm wary of taking this statement as a given, especially with such a weak reference. My question is simple: Is this condition true and, if so, under what rationale (i.e. why) does a dataset disqualify itself from being analysed using both exploratory and confirmatory perspectives? A more solid reference would be a good start.
