Skip to main content

Table 1 Study population and participation rates by study sample groups

From: A telephone survey of factors affecting willingness to participate in health research surveys

  Complete study population
General population sample Case–control study Cohort study Total study population
Landline Mobile telephone
Letter sent No letter All landline No letter Letter sent Letter sent
Study population approached n 1806 2194 4000 3000 200 600 7800
 Non-contact/phone number unusablea n 391 1123 1514 2005 33 77 3629
 Eligible populationb n 1415 1071 2486 995 167 523 4171
  Refusalsc 761 631 1372 540 14 122 2068
  Completed interviews n 654 440 1094 455 153 401 2103
  Participation rate % 46.2 41.1 44.0 45.7 91.6 76.7 50.4
  1. aIncludes no answer, engaged, answering machine, those under 18, those with language difficulty and too frail/old/ill
  2. bExcludes non-contacts
  3. cIncludes those who actively declined or claimed to have already done the survey, or made but did not keep an appointment, or terminated during the survey, or said that they did not know the named person or who asked to be removed from the list