One tail vs two tail results using Hayes Process Mediational analysis

Posted by msherman on Jun 09, 2016; 2:51pm
URL: http://spssx-discussion.165.s1.nabble.com/One-tail-vs-two-tail-results-using-Hayes-Process-Mediational-analysis-tp5732365.html

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

 

[hidden email]

410-617-2417 tel

410-617-5341 fax

 

===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD