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Table 3 Random-effects meta-analysis results of randomized and non-randomized controlled trials

From: A systematic review and meta-analysis of the effectiveness of food safety education interventions for consumers in developed countries

Meta-analysis sub-groupa No. participants/trials/studies No. (%) trials with combined outcome measuresb Effect measure Effect estimate average (95 % CI)M/median (range)R,c I 2 GRADEd
RCT
 Educational training/courses
  Adults-Behaviourse 709/4/4 2 (50) SMD 0.68 (−0.06, 1.41)R 94 % Low
  Adults-Knowledge 596/3/3 0 (0) SMD 0.87 (−0.05, 1.29)R 93 % Very low
  Children/youth-Behaviours 6379/2/2 1 (50) SMD 0.20 (0.05, 0.35)R 96 % High
 Media campaigns/other messaging
  Adults-Behavioural intentions 117/2/2 1 (50) SMD 0.36 (0.02, 0.69)M 0 % Moderate
  Adults-Behaviours 686/4/4 1 (25) SMD 0.24 (−0.17, 1.03)R 85 % Low
  Adults-Knowledge 528/3/3 0 (0) SMD 0.42 (0.03, 0.92)R 82 % Low
  Adults-Attitudes 4914/8/8 4 (50) SMD 0.34 (0.05, 0.76)R 94 % Low
NRT
 Educational training/courses
  Adults-Behaviourse 1099/4/2 0 (0) SMD 0.37 (0.08, 0.66)M 58 % Low
  Adults-Knowledge 1356/5/3 0 (0) SMD 0.44 (0.12, 1.14)R 82 % Low
  Adults-Attitudes 778/4/2 1 (25) SMD 0.26 (0.10, 0.43)M 0 % Moderate
  Children/youth-Behaviours 329/3/2 0 (0) SMD 0.33 (0.17, 0.90)R 64 % Very low
  Children/youth-Knowledge 339/3/2 0 (0) SMD 0.24 (0.14, 0.73)R 75 % Very low
 Media campaigns/other messaging
  Adults-Behaviours 1118/2/2 0 (0) RR 2.31 (1.30, 3.33)R 90 % Low
  Adults-Attitudes 1442/3/3 1 (33) RR 1.75 (1.01, 2.85)R 95 % Very low
  1. RCT randomized controlled trials, NRT non–randomized controlled trials, SMD standardized mean difference (Hedges’ g), RR relative risk, CI confidence interval
  2. aSubgroups divided by study design, intervention type, target population, and outcome type
  3. bRefers to studies that reported multiple measures of the same construct in the same individuals, which were combined post hoc into one overall measure
  4. cSuperscript M indicates that an average estimate of effect and 95 % CI is provided because heterogeneity was low to moderate (I2 = 0–60 %). Superscript R indicates that the median and range of study effect sizes is provided because heterogeneity was high (I2 > 60 %)
  5. dExplanation of the GRADE ratings:
  6. Very low = the true effect is likely to be substantially different from the measured estimate
  7. Low = the true effect may be substantially different from the measured estimate
  8. Moderate = the true effect is likely to be close to the measured estimate, but there is a possibility that it is substantially different
  9. High = strong confidence that the true effect lies close to that of the measured estimate
  10. eOne trial/study in each of these analyses used an imputed pre-post correlation value of 0.83 from Kendall et al. (2004) [37]. In both cases, sensitivity analyses indicated that the selection of the imputed value had an appreciable impact on the meta-analysis results (Additional file 12), leading to a downgrading of these findings in the GRADE assessment (Additional file 10)