[Mediation-information] Sensitivity analysis

[Kosuke Imai]

Alina,

  For the examples of sensitivity analyses, you should look at our APSR
paper.  Our psychological methods paper also has some examples too.  For
the post-treatment variable issue, here is the paper you can look at:
http://imai.princeton.edu/research/medsens.html  The procedure is
implemented in the R package too:
http://imai.princeton.edu/research/files/mediationR2.pdf

Best,
Kosuke

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


On Fri, Aug 15, 2014 at 9:51 AM, Feinholdt, A. <A.Feinholdt at uva.nl> wrote:

>  Dear Kosuke,
>
>  a couple of days ago, I was in contact with you concerning a STATA code
> for the sensitivity analysis. Fortunately, I was able to understand and run
> the R code. However, I am currently facing two problems: Since your
> analysis is still new, there are only a handful of studies which use the
> sensitivity analysis to strengthen their results. However, from these
> studies it is unclear what and how to report findings from the sensitivity
> analysis. Therefore, I would like to seek your advice on this matter.
> That is, what do you think is essential to be reported from a sensitivity
> analysis?
>
>  The other problem concerns my findings: The goal of my study (an
> experimental online survey in which participants were randomly assigned to
> one of four conditions) was to show that framing effects would be serially
> mediated through two emotions. To support the validity of a serial
> mediation, I have first run a "normal" causal mediation analysis with R
> while ignoring the possibility of a potential post-treatment confounder.
> Here the findings supported the notion of an ACME through one of the two
> emotions. Next, I have tested the causal mediation analysis with
> confounding by an alternative pathway. This analysis demonstrated that ACME
> was no longer significant - neither in the treatment nor in the control
> group. As such, I have concluded that the initial assumption was no longer
> tenable once the post-treatment confounder was accounted for. In addition,
> I have argued that under conditions like these it would be important to
> refer to other analytical strategies such as the serial mediation analysis
> - since this one does not presupposes causal independence between pathways.
> I can assume that this description is pretty vague but it may be enough
> for you to conclude, whether the sensitivity analysis can be used to
> support the application of a serial mediation analysis or not?
>
>  I can imagine that you have a busy schedule but maybe you can find some
> time to consult me on the aforementioned issues.
> Thanks in advance for reading my e-mail and I hope to hear from you.
>
>  Best wishes,
> Alina Feinholdt
>  *PhD candidate*
> *Amsterdam School of Communication Research*
>
>
>
>
>  ------------------------------
> *Von:* Kosuke Imai [kimai at princeton.edu]
> *Gesendet:* Mittwoch, 6. August 2014 11:34
> *An:* Feinholdt, A.
> *Betreff:* Re: STATA - sensitivity analysis
>
>   Dear Alina,
>
>    Unfortunately, we don't have this code in STATA.  But, you can use our
> R package, which is pretty straightforward even if you don't know much
> about R.  Try this tutorial, which gives you a step-by-step instruction:
> http://imai.princeton.edu/research/files/mediationR2.pdf
>
>  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 Wed, Aug 6, 2014 at 3:52 AM, Feinholdt, A. <A.Feinholdt at uva.nl> wrote:
>
>>  Dear prof. Imai,
>>
>>  my name is Alina Feinholdt and I am a PhD student at the University of
>> Amsterdam, the Netherlands. I just recently read one of your papers on
>> "Identification and Sensitivity Analysis for Multiple Causal Mechanisms:
>> Revisiting Evidence from Framing Experiment". Since I am dealing myself
>> with potential post-treatment confounders (two emotions are studied as
>> pathways following news framing), I would like to run both the mediation
>> effect analysis and the sensitivity analysis with STATA. However, so far I
>> could only find an R code dealing with causally dependent multiple
>> mechanisms. My question is now if you also have a STATA code that would
>> allow me to run an analysis for causally dependent multiple mechanisms? If
>> not is there another way of running the same analysis with the STATA? That
>> is, which calculations would I need to do in order to analyse my data for
>> potential post-treatment confounders?
>>
>>  I would much appreciate your response as I currently do not know who
>> else could help me with it.
>>
>>  Best wishes,
>> Alina Feinholdt
>>   *PhD candidate*
>> *Amsterdam School of Communication Research*
>>
>>  *Universiteit van Amsterdam*
>> *Kloveniersburgwal 48,*
>> *1012 CX Amsterdam, *
>> *The Netherlands*
>>
>>
>
>
>
>
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