Deliverable D 1.3 RESULTS OF META-ANALYSIS ... - cast-eu.org

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Campaigns and awareness raising strategies in traffic safety — <strong>Deliverable</strong> D-1.1Table 8.1. Candidate variables for the explanation of campaign effects on accidents. Each iscategorical. Variables with more than two levels were coded as dummy variables, so count asmore than one variable. For example, [theme] was recoded as [drink-drive] (yes/no),[speeding] (yes/no) and [general] (yes/no). All yes/no variables were then coded as yes = 1and no = 0. Scale was coded as national campaign= 1; other level of campaign = 0.background[decade] before / after 2000[theme] drink-drive / speeding / general / others[scale] national / others[duration] 0-29 days / 30-200 days / othersdelivery[combined mass-media] Did the campaign use television+radio+newspaper? yes /no[personal influence] Did the campaign attempt to influence personally? yes / no[on-road] Did campaign use billboards, variable/fixed message signson the road? yes / no[dvd-video-cinema] Did campaign use either DVD, video or cinema? yes / no[target identification] Was a particular group defined and targeted? yes / no[enforcement] Was the campaign accompanied by enforcement? yes / nocontent[emotional and rational] Did campaign have emotional and rational content? yes / no[non-shockingconsequences]Did the campaign show non-shocking consequences? yes/no[social norm] Did the campaign address the social norm? yes / no[previous campaign] Was the content based on previous campaigns? yes / no[risk of detection] Did the campaign attempt to point out the risks of beingdetected? yes / no[risk of harm] Did the campaign attempt to point out the risks of beingharmed? yes / no[target group consulted] Did the campaign consult a sample of the target group indeveloping the content? yes / noThis model was developed by considering the statistical properties of eachvariable. Inspection of the bivariate correlations among the explanatoryvariables revealed a strong correlation between [risk of detection] and[enforcement] (r = 0.73; p < 0.001). The former variable was excluded fromthe model because we wished to compare associations between enforcementand accident counts with those found in previous projects (Delhomme et al,1999; Vaa et al., 2004).At this stage the model comprised 19 variables 32 . To improve the efficiency ofthe model, zero-order correlations, subgroup analyses and output of an initialsimultaneous regression run (to examine tolerance relationships amongvariables) were again consulted and discussed by the project team, with aview to capture important influences on campaign effects in the most efficientway. The following variables were excluded at this stage: [duration 29 to 200days], [theme-speeding], [theme-general], [dvd-video-cinema], [target groupconsulted] and [previous campaign].The remaining 13 variables were then checked for missing cases. A furtherfive variables were excluded on the basis that they contained more than 532 Variables containing more than two levels were dummy coded so are actuallycounted as more than one variable.102
Campaigns and awareness raising strategies in traffic safety — <strong>Deliverable</strong> D-1.1missing cases. These were [emotional and rational], [non-shockingconsequences], [social norm], [target group identified] and [risk of harm].Although we considered these important, there simply was not enoughinformation across the evaluation studies to score these campaign variablessufficiently.The eight remaining variables met statistical recommendations for the ratio ofvariables studied to outcome effects in the sample (Tabachnikk & Fidell,2007).A weighted, simultaneous standard multiple regression was therefore runusing the variables [duration-0 to 29 days], [decade-after 2000], [theme-drinkdriving],[scale-national], [onroad], [personal influence], [enforcement] and[combined mass-media], using ln odds ratios calculated using accident effects(see chapter 7). An inspection of the contributions to outcome variance thenled to the exclusion of the variable [scale-national] to give a final model ofseven variables (Table 8.2).Table 8.2. Results from standard multivariate regression analysis of the final accident model.Variables, their standardised (beta) coefficients, t-values and probabilities are shown.VariableBetacoefficientt-value p-value Semi-partialcorrelation(constant) -- 1,18 .241 --[duration - 0 to 29 days] -.21 2.06 .0042 -.17[after 2000] +.21 4.27
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Deliverable D 1.3 RESULTS OF META-ANALYSIS ... - cast-eu.org

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