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document
Chocolate frogs do not increase completion of parent survey : randomised study . Four months into a year-long , national survey assessing parents ' experiences of a child 's diagnosis of autism spectrum disorder , our response fraction was only 23 % . We aimed to determine whether including a chocolate incentive in the postal survey would increase the response fraction . Families enrolled between 15 March and 25 May 2012 were randomised to receive a chocolate frog versus no chocolate frog . Both groups received a written reminder and replacement survey 2 weeks after the survey was posted and up to two telephone reminders thereafter . We analysed the effect of the incentive using χ ( 2 ) tests for the categorical response variable and t-tests for the continuous reminder and length of response variables at the end of ( i ) randomisation and ( ii ) the study ( 1 November 2012 ) . A total of 137 families were randomised in the 6-week period . Parents who received an incentive were more likely to return a completed survey in the 6 weeks than those who did not ( 21 % vs. 6 % , P = 0.009 ) . This effect faded by the end of the study ( 53 % vs. 42 % , P = 0.4 ) . There were no differences between groups at either follow-up in the number of reminders that parents received or the number of days it took parents to return the survey . Including a chocolate-based incentive does not significantly increase response rate in a postal survey over and above standard reminder techniques like posting follow-up survey packs or phoning families .
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Intervention_Educational
Chocolate frogs
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Intervention_Educational
chocolate incentive
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Intervention_Educational
chocolate frog
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Intervention_Physical
versus
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Intervention_Control
no chocolate frog
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Intervention_Educational
written reminder
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Outcome_Other
increase the response fraction .
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Outcome_Other
effect
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Outcome_Other
χ ( 2 ) tests
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Outcome_Other
and t-tests
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Outcome_Mental
received
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Outcome_Mental
number
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Outcome_Other
significantly increase response
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Participant_Age
Families
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Participant_Sample-size
A total of 137 families