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Table 3 Health care surveys that compared identifiable and non-identifiable surveys

From: Effect of numbering of return envelopes on participation, explicit refusals, and bias: experiment and meta-analysis

Author, year Population Survey topic Intervention Control
King, 1970 College students Drug use Coded questionnaire Non-coded questionnaire
King, 1970 College students Drug use and attitudes
Campbell, 1990 General population AIDS knowledge Numbering with warning of reminders Non-numbered questionnaire
Akl, 2011 Residency program directors (Family medicine) Characteristics of residency program Questionnaire numbered “to avoid sending reminders” Non-numbered questionnaire
Akl, 2011 Residency program directors (Internal medicine)
Kundig, 2011 Hospital staff Patient safety culture Numbered questionnaire Non-numbered questionnaire
This study Hospital doctors and nurses Regret associated with health care Numbered envelope Non-numbered envelope
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