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<p>No they are not. It is time once again to post my FAQ on voluntary response surveys: </p>
<p>VOLUNTARY RESPONSE POLLS </p>
<p>One professor of statistics, who is a co-author of a highly regarded AP statistics textbook, has tried to popularize the phrase that “voluntary response data are worthless” to go along with the phrase “correlation does not imply causation.” Other statistics teachers are gradually picking up this phrase.</p>
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<p>-----Original Message-----mailto:SMTPfv2@cornell.edu ”>SMTPfv2@cornell.edu</a>]mailto:apstat-l@etc.bc.ca ”>apstat-l@etc.bc.ca</a>; Kim Robinsonmailto:mmbalach@mtu.edu ”>mmbalach@mtu.edu</a>
<p>Sorry Kim, but it just aint so. Voluntary response data are <em>worthless</em>. One excellent example is the books by Shere Hite. She collected many responses from biased lists with voluntary response and drew conclusions that are roundly contradicted by all responsible studies. She claimed to be doing only qualitative work, but what she got was just plain garbage. Another famous example is the Literary Digest “poll”. All you learn from voluntary response is what is said by those who choose to respond. Unless the respondents are a substantially large fraction of the population, they are very likely to be a biased – possibly a very biased – subset. Anecdotes tell you nothing at all about the state of the world. They can’t be “used only as a description” because they describe nothing but themselves.
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