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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