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Meta-Analysis of the Effectiveness of Incentives in Organizational Surveys

Meta-Analysis of the Effectiveness of Incentives in Organizational Surveys. Vanessa Torres van Grinsven & Joop Hox. Faculty of Social and Behavioural Sciences Department of Methodology and Statistics. Incentives are widely used in individual or household surveys

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Meta-Analysis of the Effectiveness of Incentives in Organizational Surveys

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  1. Meta-Analysis of the Effectiveness of Incentives in Organizational Surveys Vanessa Torres van Grinsven & Joop Hox • Faculty of SocialandBehavioural Sciences • Department of MethodologyandStatistics Methodology and Statistics | Meta-Analysis of the Effectiveness of Incentives in Organizational Surveys |

  2. Incentives are widelyused in individual or householdsurveys • Proven methodtoimprove response rates in these surveys • But they are typicallynotused in official (business ) surveys • Systematic synthesis of experimental research on the effectiveness of incentives in organizational surveys is still lacking • Meta-analysis of the effect sizes of incentives in experimental research. • Faculty of SocialandBehavioural Sciences • Department of MethodologyandStatistics Introduction Methodology and Statistics | Meta-Analysis of the Effectiveness of Incentives in Organizational Surveys |

  3. Effect size (ES) makesstatistical meta-analysis possible • It is the dependentvariable • Represents the magnitude anddirection of the relationship of interest • Must be able to calculate a standard error for that type of ES • The standard error is needed to calculate the ES weights, called inverse variance weights • Because all meta-analytic analyses are weighted taking into account sample size. • More information: Lipsey & Wilson (2001) • In this case the effect size is the difference in response ratebetween the treatment groupsand the corresponding control groups • Faculty of SocialandBehavioural Sciences • Department of MethodologyandStatistics Short introduction on statistical meta-analysis Methodology and Statistics | Meta-Analysis of the Effectiveness of Incentives in Organizational Surveys |

  4. Search strategy: • Search made in numerous databases: e.g. Web of Science, WorldCat, EBSCO, Picarta, PsycInfo, SIAM, ESOMAR (the research papers database), AAPOR (Survey Practice database). • Search words: incentive, survey, experiment • Eligibility criteria: • Experiment with split ballot • Appropiate control group • RR1 reported or calculable • Sample sizeandgroupsizes are reported • Organizational survey • Incentives • Faculty of SocialandBehavioural Sciences • Department of MethodologyandStatistics Data collection Methodology and Statistics | Meta-Analysis of the Effectiveness of Incentives in Organizational Surveys |

  5. Organizational survey defined as survey on: • A commercial population: “Commercial populations are defined as those composed of commercial, industrial, administrative and/or business respondents who receive a questionnaire at their place of employment” Pressley & Tullar, 1977, p. 108. • Non-profit organizations • Other professionals whoreceive the questionnaire at theirplace of employmentandabout job-related issues. • Incentive: a prepaid or promised monetary or non-monetary incentive. • Faculty of SocialandBehavioural Sciences • Department of MethodologyandStatistics Methodology and Statistics | Meta-Analysis of the Effectiveness of Incentives in Organizational Surveys |

  6. Studycharacteristicswerecodedtounderstandifthey had an effect on the effect size • Codingschemebased on open codingandcodingschedulesby De Leeuw et al. (2007) andHox & De Leeuw (1994) • Also effect size information was coded (the response rates) • Codedstudy features were: year of publication, country, research organization, sample frame, population type, survey topic, survey method, data type, industry, respondent type, voluntary or mandatory survey, type of incentive, andvalue of the incentive. • Additionally(incentive): prepaid vspromised, monetaryvsnonmonetary, type of monetary incentive, type of nonmonetary incentive. • Faculty of SocialandBehavioural Sciences • Department of MethodologyandStatistics Coding of studycharacteristics Methodology and Statistics | Meta-Analysis of the Effectiveness of Incentives in Organizational Surveys |

  7. 34 studies with a total of 68 experimentalconditions. • Combined sample size of 343.500 respondents including the control groups. • The response rates are expressed as proportions, which are then transformed into Z-values using the standard normal distribution. • The standardized effect size d is then given by: • Faculty of SocialandBehavioural Sciences • Department of MethodologyandStatistics Data analysis (1) Methodology and Statistics | Meta-Analysis of the Effectiveness of Incentives in Organizational Surveys |

  8. And the standard error of d is given by: • Because a larger standard error corresponds to a less precise effect size value, the optimal weights are computed as the inverse of the squared standard error value – hence inverse variance weight (Hedges 1982; Hedges & Olkin, 1985): • Faculty of SocialandBehavioural Sciences • Department of MethodologyandStatistics Data analysis (2) Methodology and Statistics | Meta-Analysis of the Effectiveness of Incentives in Organizational Surveys |

  9. Inverse varianceweighted meta-analysis techniqueswith a random effects model withrestricted maximum likelihoodestimation (REML) • The distribution of effect sizes was heterogeneous • Meta-regressionand the meta-analyticanalogue of ANOVA wereusedfor the moderator analysis • SPSS Wilson’s meta-analysis macros (http://mason.gmu.edu/~dwilsonb/ma.html ) • More information Lipsey & Wilson (2001) Data analysis (3) Methodology and Statistics | Meta-Analysis of the Effectiveness of Incentives in Organizational Surveys |

  10. A relevant issur in meta-analysis is publication bias • It refersto the possibilitythat relevant studies mightnot have been published, but disappeared in the file-drawer • Publication bias was assessedbyinspecting a funnel plot andcalculating the fail-safe N. • Fail-safeN: the significant effect of the incentive on the response rate would be swiped away if we assume the existence of 426 unpublished studies all reporting no effect highly implausible • Faculty of SocialandBehavioural Sciences • Department of MethodologyandStatistics Publication bias Methodology and Statistics | Meta-Analysis of the Effectiveness of Incentives in Organizational Surveys |

  11. Faculty of SocialandBehavioural Sciences • Department of MethodologyandStatistics Publicationbias:Funnel plot of the correlation between effect size and sample size Methodology and Statistics | Meta-Analysis of the Effectiveness of Incentives in Organizational Surveys |

  12. Sending or promisingan incentive does have a small but significant effect on the response rate • Mean effect sized = .25 (p<.0001) • In terms of Cohen’s (1988) effect sizedefinitionsthis is a small effect • Of all the codedstudy features onlyresearch organizationhad a significant effect on the effect size (p=.04) • Commercial organizations: d = .36 • Universities: d = .26 • Governmentalinstitutions: d = .10 • Faculty of SocialandBehavioural Sciences • Department of MethodologyandStatistics Results Methodology and Statistics | Meta-Analysis of the Effectiveness of Incentives in Organizational Surveys |

  13. Faculty of SocialandBehavioural Sciences • Department of MethodologyandStatistics Value of the incentive: Effect size (d) related to the amount of the monetary incentive Methodology and Statistics | Meta-Analysis of the Effectiveness of Incentives in Organizational Surveys |

  14. The largest effect canbeexpected in commercial surveys; the smallest in surveysbygovernment-relatedinstitutions, likeNSOs. • If we include the response rate as a predictor, the significant differencesbetweenorganization types disappearscompletely; while the regressioncoefficientfor the response rate is negativeandhighly significant • Thus: research organizations that already are obtaining high response rates, find it difficult to increase them further • We concludethat incentives canbeused as a general tool toincrease response in organizationalsurveyswith different survey features • Faculty of SocialandBehavioural Sciences • Department of MethodologyandStatistics Results Methodology and Statistics | Meta-Analysis of the Effectiveness of Incentives in Organizational Surveys |

  15. Whatseems important thus is not the factualvalue(as in aneconomic exchange) • But the psychologicalvalue: • Reciprocitytheory(Gouldner, 1960): • a symbolic gift thatneedstobereciprocated: • A recipientmay feel obligatedtoreciprocatebycompleting the questionnaire • Cost/benefit theory(e.g. Singer, 2011): • The incentive is seen as a symbolic benefit that counteracts the perceivedcosts of completingandreturning the questionnaire • Faculty of SocialandBehavioural Sciences • Department of MethodologyandStatistics Discussion Methodology and Statistics | Meta-Analysis of the Effectiveness of Incentives in Organizational Surveys |

  16. Cohen, J. (1988). Statistical power analysis for the behavioral sciences. Hillsdale, NJ: Erlbaum • De Leeuw, E., Callegaro, M., Hox, J., Korendijk, E. & Lensveldt-Mulders G. (2007). The Influence of Advance Letters on Response in Telephone Surveys: A Meta-Analysis. Public Opinion Quarterly, 71(3), 413-443. • Gouldner, A. W. (1960). The norm of reciprocity: A preliminary statement. American Sociological Review, 25, 161-178. • Hedges, L.V. (1982). Estimating effect size form a series of independent experiments. Psychological Bulletin, 92, 490-499. • Hedges, L.V. and Olkin, I. (1985). Statistical methods for meta-analysis. Orlando, Florida: Academic Press. • Hox, J.J., & De Leeuw, E.D. (1994). A comparison of nonresponse in mail, telephone, and face-to-face surveys. Applying multilevel modeling to meta-analysis. Quality and Quantity, 28, 329-344. • Lipsey, M.W. & Wilson, D.B. (2001). Practical Meta-Analysis. Sage Publications. • Pressley, M.M. & Tullar, W.L. (1977). A Factor Interactive Investigation of Mail Survey Response Rates from a Commercial Population. Journal of Marketing Research, 14(1), 108-111. • Singer, E. (2011). Toward a Benefit-Cost Theory of Survey Participation: Evidence, Further Tests, and Implications. Journal of Official Statistics, 27, 379-392. • Faculty of SocialandBehavioural Sciences • Department of MethodologyandStatistics References Methodology and Statistics | Meta-Analysis of the Effectiveness of Incentives in Organizational Surveys |

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