[Mediation-information] Effect size from Mediation software

[Kosuke Imai]

Xiayi,

  I would not recommend odds ratio as a quantity of interest.  I realize that this is a typical quantity of interest reported in some fields, but nobody was able to give me an intuitive interpretation of that quantity.  The problem is that odds ratio is a ratio of two ratios.  If I ask you "what does it mean to have odds ratio of 3?", can you answer it intuitively so that general audience without technical training can understand it easily?  I doubt it.  Rather, you should report the risk differences as it is done in our software.  Any patient can understand the statement that "your risk of death increases by 3 percentage points" but they have no idea if you tell them "your odds ratio of death is 3".

Best,
Kosuke

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

On Nov 26, 2013, at 3:53 AM, "Ke, Xiayi" <x.ke at ucl.ac.uk> wrote:

> Dear Dustin and Kosuke,
> 
> I am sorry if I have been unreasonably persistent.
> 
> I have explained to others more or less along the lines as suggested in your email and the two 2010 papers (e.g. Equation 1 and 2, Table 5, Appendix D etc from the Imai, Keele and Tingley paper) , but they wanted a more intuitive answers like the odds ratio type or percentage of effect.
> 
> Many thanks for your help and your excellent work.
> 
> BW,
> 
> Xiayi.
> 
> 
> On Mon, Nov 25, 2013 at 9:49 PM, Kosuke Imai <kimai at princeton.edu> wrote:
> Hi Xiayi,
> 
>  The estimates are average causal mediation effect estimates.  They do not necessarily correspond to coefficients.  Have a look at this paper which gives a non-technical overview of causal mediation analysis: http://imai.princeton.edu/research/mediationP.html or http://imai.princeton.edu/research/BaronKenny.html
> 
> Best,
> Kosuke
> 
> ---------------------------------------------------------
> Kosuke Imai               Office: Corwin Hall 036
> Professor                 Phone: 609-258-6601
> Department of Politics    Fax: 609-258-1110
> Princeton University      Email: kimai at Princeton.Edu
> Princeton, NJ 08544-1012  http://imai.princeton.edu
> ---------------------------------------------------------
> 
> On Nov 25, 2013, at 12:47 PM, Ke, Xiayi <x.ke at ucl.ac.uk> wrote:
> 
>> Dear Kosuke Imai,
>> 
>> I have been using your mediation analysis methods and software recently. I am wondering whether you can kindly advice me when the non-parametric bootstrapping option is used, what are the effect size "estimates" standing for, how are they obtained (from standardized regression coefficient beta?), and what is the best way to interpret them? I guess their values can only vary between 0 and 1?
>> 
>> I look forward to hearing from you.
>> 
>> BW,
>> 
>> Xiayi.
> 
> 
> _______________________________________________
> Mediation-information mailing list
> Mediation-information at lists.r-forge.r-project.org
> https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/mediation-information