What is it?
A social incentive such as a personalised table of questionnaire response to date to evidence previous responses noted and valued are included in the cover letter.
Does it work?
Including a social incentive in the cover letter may result in little or no difference to retention.
How big is the effect?
An increase of -1% (95% confidence interval = -4% to 2%).
How certain are we?
GRADE Low certainty.
We recommend that trialists include a social incentive in cover letters in the context of an intervention evaluation.
How can I use this straight away?
See Resource bundle below for details on how to use social incentives.
Imagine initial retention is 65% of those approached. You have a trial with 100 participants that needs responses from 80 to meet its statistical power calculations. Retention of 65% means that you will be 15 responses short (see chart below).
Now imagine using a social incentive. The chart below shows the impact of an absolute increase of -1% (95% CI = -4% to 2%). Retention is now 64%, which means our best estimate is that you would now be 14 responses short.
*Random effects model done using Comprehensive Meta-Analysis v4 (www.meta-analysis.com).
Differences >0% favour the intervention. The GRADE assessment is low because of the imprecision of a single study and a wide CI crossing RD=0.
How to Cite
Citation: Ostrovska B. Evidence pack– Retention: Social incentive (RET20), 2023, https://www.trialforge.org/retention-sector/social-incentive-id-ret20/.
- This summary is from the Cochrane review of strategies to improve retention in randomised trials (https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.MR000032.pub3/full).
- The ‘Does it work?’ statement is structured according to effect size and GRADE certainty as per GRADE Guidelines 26 (https://doi.org/10.1016/j.jclinepi.2019.10.014). The statement is for trivial effect size and Low GRADE certainty.
- The recommendation statement is the consensus view of the authors of this summary based on the GRADE certainty and features of the trials contributing to the evidence.
- If you have any questions contact email@example.com.