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Mediation
Mediation Analysis — Mindfulness → Stress → Anxiety
Baron-Kenny mediation with bootstrap CI. Indirect effect a×b = −3.97. Stress mediates 50.9% of the mindfulness–anxiety path.
📊 Indirect ab = −3.97, BootCI [−6.12, −1.94]
Step-by-step solution
🔄 18 · Mediation Analysis
Mindfulness Training → Perceived Stress → Anxiety
Mediation
Research Question:
Does mindfulness training (X) reduce anxiety (Y) indirectly through its effect on perceived stress (M)? N=90 adults (45 per group).
| Path | Description | b | SE | t | p |
|---|---|---|---|---|---|
| a | Training → Stress (X→M) | −6.40 | 1.30 | −4.92 | <.001 |
| b | Stress → Anxiety (M→Y, controlling X) | 0.62 | 0.11 | 5.64 | <.001 |
| c | Total: Training → Anxiety (X→Y) | −7.80 | 1.90 | −4.11 | <.001 |
| c' | Direct: Training → Anxiety (controlling M) | −3.83 | 1.82 | −2.11 | .037 |
Indirect Effect (mediated via stress)
$$\text{Indirect effect}=a\times b=(-6.40)\times(0.62)=\mathbf{-3.97}$$
$$\text{Bootstrap 95\% CI for }ab:\;[-6.12,\;-1.94]\quad\text{(excludes 0 → significant mediation)}$$
$$\text{Proportion mediated}=\frac{|ab|}{|c|}=\frac{3.97}{7.80}=\mathbf{50.9\%}$$
−3.97
Indirect ab
[−6.12, −1.94]
Bootstrap 95% CI
50.9%
% Mediated
✅ Significant partial mediation — 51% of the total training effect on anxiety is transmitted through stress reduction. The direct effect c' remains significant, indicating both direct and indirect pathways.
APA-7
A simple mediation model (PROCESS Macro, Model 4) tested whether perceived stress mediated the effect of mindfulness training on anxiety. The indirect effect was significant, ab = −3.97, 95% bootstrap CI [−6.12, −1.94], accounting for 50.9% of the total effect. A significant direct effect also remained, c' = −3.83, SE = 1.82, p = .037, indicating partial mediation.
💡
Full mediation: direct effect c' is non-significant after controlling M. Partial mediation: c' remains significant. Use bootstrapped CIs (not Sobel test) — APA recommends 5,000 bootstrap samples.