[Mediation-information] interpretation for mediation effect

[Kosuke Imai]

This quantity is defined as:

(Total Effect - ACME) / Total Effect

And so in your case, it looks like the direct effect has the opposite sign.

Kosuke

Department of Politics
Princeton University
http://imai.princeton.edu


On Oct 5, 2011, at 10:17 PM, Weichao Bao wrote:

> Dear All,
> 
> I have one more question about the interpretation of the Proportion of Total Effect via Mediation (Average). For example in the following result,
> Proportion of Total Effect via Mediation (Average):  -0.1391 95 % CI  -1.7258  0.8114  
> Does it mean the 13.91% of total effect is mediated by the mediator? Can I interpret the proportion here as a percentage?
> 
> Thanks a lot.
> 
> Sincerely,
> Weichao 
> 
> On Thu, Sep 15, 2011 at 10:55 AM, Weichao Bao <weichaobao at gmail.com> wrote:
> Dear All,
> 
> 
> 
> I am using the mediation package on my research. The outcome is dichotomous and the treatment is continuous. It was run with GAM model.  But I am confused with the following results. It shows all the Mediation Effect_0, Mediation Effect_1,and Mediation Effect (Average) have significant mediation effect based on 95% CI. However, the Proportion of Total Effect via Mediation_0, Proportion of Total Effect via Mediation_1, and Proportion of Total Effect via Mediation (Average) indicate there is no mediation at all based on the 95% confidence interval.  The result is: 
> 
> 
> 
> Mediation Effect_0:  -0.004309 95 % CI  -0.0086640 -0.0007235
> 
> Mediation Effect_1:  -0.006557 95 % CI  -0.014173 -0.001015
> 
> Direct Effect_0:  0.04452 95 % CI  0.001001 0.112969
> 
> Direct Effect_1:  0.04228 95 % CI  0.0009312 0.1061973
> 
> Total Effect:  0.03797 95 % CI  -0.004335  0.101359
> 
> Proportion of Total Effect via Mediation_0:  -0.1069 95 % CI  -1.592  0.817
> 
> Proportion of Total Effect via Mediation_1:  -0.1701 95 % CI  -1.8595  0.8059
> 
> Mediation Effect (Average):  -0.005433 95 % CI  -0.011059 -0.000928
> 
> Direct Effect (Average):  0.0434 95 % CI  0.0009659 0.1098405
> 
> Proportion of Total Effect via Mediation (Average):  -0.1391 95 % CI  -1.7258  0.8114 
> 
> 
> 
> Can somebody help me to explain this?
> 
> 
> 
> Thanks a lot.
> 
> Sincerely,
> 
> 
> Weichao
> 
> 
> 
> 
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