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Table 3 Mediation effects of changes in psychosocial factors on changes in fat intake

From: Explaining the effects of a 1-year intervention promoting a low fat diet in adolescent girls: a mediation analysis

Psychosocial factor Single-mediator models
  α(SE) β(SE) αβ(SE) 95% CI of αβ z % mediated effect
Attitude -0.004 (0.031) -7.773 (2.077)*** 0.031 (0.241) -0.441, 0.503 0.129 statistical suppressiona
Self-efficacy -0.020 (0.077) -1.790 (1.581) 0.036 (0.139) -0.236, 0.308 0.258 statistical suppressiona
Social support 0.005 (0.098) -2.548 (1.732) -0.013 (0.250) -0.502, 0.477 -0.051 0.1
Perceived benefits 0.069 (0.039) -1.799 (2.997) -0.124 (0.113) -0.345, 0.097 -1.099 1.4
Perceived barriers 0.067 (0.022)** 2.260 (1.493) 0.151 (0.060)* 0.034, 0.268 2.535 suppression
  Multiple-mediator model
  α(SE) β(SE) αβ(SE) 95% CI of αβ z % mediated effect
Attitude -0.004 (0.031) -6.966 (1.866)*** 0.028 (0.054) -0.078, 0.134 0.515 statistical suppressiona
Self-efficacy -0.020 (0.077) -0.379 (1.941) 0.008 (0.040) -0.070, 0.085 0.191 statistical suppressiona
Social support 0.005 (0.098) -1.643 (2.177) -0.008 (0.037) -0.080, 0.060 -0.223 0.1
Perceived benefits 0.069 (0.039) -0.144 (3.055) -0.010 (0.211) -0.423, 0.403 -0.047 0.1
Perceived barriers 0.067 (0.022)** 0.786 (1.741) 0.053 (0.117) -0.177, 0.282 0.450 statistical suppressiona
  1. α estimate of intervention effect (unstandardized regression coefficient) on residualized change score of psychosocial factors
  2. β estimate of the independent effect of the mediator (unstandardized regression coefficient of residualized change scores) on residualized change score for fat intake αβ product-of-coefficient estimate; mediated effect
  3. SE standard error
  4. 95% CI of αβ 95% confidence interval of the mediated effect
  5. z standard deviate associated with mediated effect (used for significance testing)
  6. * significant at the 5% probability level, ** significant at the 1% probability level; *** significant at the 0.1% probability level
  7. a Statistical suppression refers to a statistically non-significant indirect effect that is opposite in sign to the intervention effect