LISTSERV at the University of Georgia
Menubar Imagemap
Home Browse Manage Request Manuals Register
Previous messageNext messagePrevious in topicNext in topicPrevious by same authorNext by same authorPrevious page (August 1997)Back to main SPSSX-L pageJoin or leave SPSSX-L (or change settings)ReplyPost a new messageSearchProportional fontNon-proportional font
Date:         Wed, 13 Aug 1997 19:37:33 GMT
Reply-To:     Richard F Ulrich <wpilib+@PITT.EDU>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@UGA.CC.UGA.EDU>
From:         Richard F Ulrich <wpilib+@PITT.EDU>
Organization: University of Pittsburgh
Subject:      Re: significance of correlation coefficient

Richard Batt ( wrote: : Hi!

: For a simple correlation (N=35) SPSS 7 for Windows gives p = 0.05 for : approx r = 0.330. However when I check by hand using, : p_val = 1 - CDF.T(t,33) where t = r * sqrt( (33/(1-r^2) ) : I get p = 0.05 for approx 0.295. Any suggestions as to why the : discrepancy? In my simulations I was doing multiple correlations, : perhaps SPSS adjusts the p value for this?

- If you are doing MULTIPLE CORRELATIONs then you are looking at multiple Rs which are inherently two-tailed. You have described your first correlation in contradictory ways, when you say "simple" and then "multiple".

The CDF gives you one tail, which yields a one-tailed p-value, as you show above.

Rich Ulrich, biostatistician Univ. of Pittsburgh

Back to: Top of message | Previous page | Main SPSSX-L page