Re: One tail vs two tail results using Hayes Process Mediational analysis

Posted by Bruce Weaver on Jun 09, 2016; 5:39pm
URL: http://spssx-discussion.165.s1.nabble.com/One-tail-vs-two-tail-results-using-Hayes-Process-Mediational-analysis-tp5732365p5732368.html

Disclaimer:  I have never used the PROCESS macro.  However, I have heard people talking about it, and based on what I've heard, I wonder if the CIs are bootstrap CIs.  If they are, and if the test is not obtained via bootstrapping, then one could easily get the kind of result you describe.

HTH.

msherman wrote

Dear List: I just used Hayes' Process macro within spss 23.0 to test for an indirect mediational effect and have a result which is a little confusing. The print out for the indirect effect shows that the 95% CI for the indirect coefficient is -0.00097 (lower Limit) and  0.25978  (Upper limit) with a Z value of 2.09 and a p value of .03641. Since the 95% CI includes zero the results are not statistically significant yet the p value is statistically significant. Is this inconsistency due the p value representing only one tail whereas the 95% CI utilizes two tails (which would relate to .03641 X 2 = .07282 and thus would include zero contained within the 95% CI)?  I looked at another result where the Z value was 0.95 and it had a p value of .34338 which, to me, suggests that this value represents .17169 in each tail or a total p value of .34338. If this is correct then the p value for the Z of 2.09 actually is .018205 in one tail and .03641 in two tails  (.018205 X 2 = .03641). If so then the 95% CI should not contain the value of zero. What am I missing?

Martin F. Sherman, Ph.D.
Professor of Psychology
Director of Master's Education: Thesis Track

Department of Psychology
222 B Beatty Hall
4501 North Charles Street
Baltimore, MD 21210

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