Thanks a lot Jason.For 2), I did test another model, that is, X-->Y-->M (it is originally X-->M-->Y, where the p value for mediation effect is about 0.01) , and now the p value for mediation effect is 0.04. It's higher that 0.01 but also significant.Does that mean that I can't (or can) be confident about my original model? But the new model X-->Y-->M seems doesn't make sense (X=age, Y=a cognitive variable, M = a brain structure) because usually we think age causes structural changes which results in changes in cognition, not the reverse?2013/4/22 Jason Steffener <[log in to unmask]>
Dear Mark,I would suggest reading papers by Preacher and Hayes about mediation. They have quite a few easy to read discussions about the procedures.And to address the reviewers points:1) This is up to you. It is only theory that can support a mediation analysis performed with cross-sectional data. Do the relationships that you are testing make sense? Is there theory to support an X-->Y relationship, an X-->M relationship, an M--Y relationship? and what does it mean that M mediates the relationship between X and Y? This needs to be clearly explained and supported with theory otherwise you have the reviewers correct concern.2) This should be explored by testing alternate models of the X,M,Y relationships. See Salthouse 2012 "Neuroanatomical substrates of age-related cognitive decline"3) This is based on the theoretical underpinnings of your model and the support that you data gives for the model.I hope this helps,JasonOn Mon, Apr 22, 2013 at 8:53 AM, Tseng Mark <[log in to unmask]> wrote:Dear Smith, can I know which paper it is? yes we do use the mediation toolbox developed by Tor Wager. Thanks a lot.2013/4/22 Stephen Smith <[log in to unmask]>
Hi - there's a nice paper by Tor Wager on that topic that I'd recommend you read?Cheers.On 22 Apr 2013, at 06:41, Mark <[log in to unmask]> wrote:Hi,
This is a followup question about a mediation analysis in our study. One of the reviewers asked for questions below and I wonder if someone could help, because I don't know how to calculate the parameter the reviewer requested. The questions are:
(1) Is the mediation analysis sensible?
(2) Can you provide an assessment of the credibility of the outcomes of the analysis?
(3) How confident are they that the result would be replicated in another sample?
How can I calculate the sensibility, credibility, and confidence?
Thanks in advance.