Regarding what I have read about mediating tests, there are three of them, including: 1) the causal steps approach, 2) Sobel test, and 3) Bootstrapping test. However, I figured out from the scholars that the best one is "bootstrapping test" because of its advantages compared with Baron and Kenny's approach and Sobel test.
I found some papers that reported two of these methods in one research (e.g. Bootstrapping and Sobel tests). I do not understand why it is necessary?!
Further, in one research, it was justified that the Sobel test is conducted to test the individual mediating effects. In other words, it is a way to compare the effects of more than two mediators and the greater values of Z (Sobel test value) shows more powerful mediating effect. But I could not find an academic source for it!
Would you please let me know whether it is right?
Thank you for your valuable time,
Dear Farimah,
Bootstrap methods have been proposed as a method for improving cutting scores for classifying observtions when local base rates for one's sample differ from the base rates for the sample upon which the original cutting scores were developed (Rorer & Dawes, 1982).
A related family of bootstrap methods involves iterative resampling of jackknife half-samples and cumulating a frequency distribution of the statistics under investigation (Stine, 1990).
Boottstrap procedures have been recommended for use in validity generalization research because of their ability to generate accurate estimates of the standard error of correlation coefficients (Switzer, Paese Drasgow, 1992).
Although bootstrap estimates may obverestimate positive predictive value when the population is low and may overstimate the base rate in applications involving a variable that has a low base rate for one of the response levels.
The leave-one-out procedure represents an extreme variation of the one-sample jacknife.
The leave-one-out procedurereduce bias that occur when estimating model performance using a single sample and is widely used in time-series and discriminant analysis and gives an almost unbiased estimate of the confidence intervals for the true classification error rate. it is also robust over violation of the normality assumption and the relative way with which it is generalized to multicategory applications.
I hope that this help you in some way.
Have a nice day
Helena
Dear Farimah,
No one was right, the State of the Art about mediation is the potential approach of Imai et al. Please see some papers:
http://psycnet.apa.org/journals/met/15/4/309/
http://www.jstor.org/stable/41058997
http://journals.cambridge.org/abstract_S0003055411000414
The software R includes packages for mediation:
http://link.springer.com/chapter/10.1007/978-1-4419-1764-5_8
http://dspace.mit.edu/handle/1721.1/91154
Also, Stata has a package for mediation, but with fewer functions.
Good luck.
Andrés.
Farimah,
There are several approaches to mediation, and some are better than others. It depends on many things, but perhaps most important is the type of variables you have in the various parts of the model.
I am attaching a paper I recently wrote on mediation analysis, where we ran several simulations for different mixes of variable types for the intervention, mediator and outcome. As you will see, some models performed better than other.
All these methods can be applied in Stata and we refer the reader to those related commands.
I hope this helps
Ariel
Article Using mediation analysis to identify causal mechanisms in di...
Dear Farimah,
For my opinion, you can choose the causal step approach for mediator modeling and then you can use the bootstrapping method to justify your finding. Usually, both of these method will be provide almost similar finding. Maybe you can read the book " A handbook of SEM" written by Zainudin Awang. The new version will be launched next month. He will explain more about the mediator and second order model.
Thank you all for your explanations and the attached files.
Wishing you all the best,
Thank you for your reply dear Prof. Al-Atwi. Would you please share with me your idea regarding the function of Sobel test mentioned in the question?
Thank you,
Best regards,
Kindly find the detail explanation of Sobel test, Kenny mediation procedure, and Bootstrapping method
Article Making Sense of Mediating Analysis: A Marketing Perspective
Dear Farimah,
Good question, I think as what you mentioned that it is not frequently researchers use these test. Recently when bootstrappying added to recent versions of SPSS, researchers start to use it. In a recent published study, {attached} We c onducted moderation and mediation tests using multiple programs and software which included SEM, SPSS, AMOS, SOBEL test,and PROCESS Macrosfor SPSS. In order to confirm if a variable is making amoderation effect in the relationship between an independent variable and a dependent variable, the nature of this relationship must change once the moderator variable changes.
you can read more detail in the attached article.
Regards
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