Journal of clinical epidemiology
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Randomized Controlled Trial
An advance letter did not increase the response rates in a telephone survey: a randomized trial.
To test the impact of an advance letter on response and cooperation rates in a nationwide telephone survey, given previous inconsistent results. ⋯ An advance letter was not seen to be effective in increasing response or cooperation rates in a nationwide telephone survey. Researchers should consider alternative methods of increasing participation in telephone surveys.