Date:         Mon, 22 Nov 1999 17:06:59 -0600
Reply-To:     "Nichols, David" <nichols@SPSS.COM>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         "Nichols, David" <nichols@SPSS.COM>
Subject:      Re: Johnson-Neyman procedure in ANCOVA

If something's been written to implement the Johnson-Neyman technique in
SPSS, I'm not aware of it.

David Nichols
Principal Support Statistician and
Manager of Statistical Support
SPSS Inc.

> -----Original Message-----
> From: Emili GARCIA-BERTHOU [mailto:caegb@XAMBA.UDG.ES]
> Sent: Monday, November 22, 1999 12:30 PM
> To: SPSSX-L@LISTSERV.UGA.EDU
> Subject: [SPSSX-L] Johnson-Neyman procedure in ANCOVA
>
>
> The standard design of analysis of covariance (ANCOVA) assumes the
> homogeneity of regression coefficients of the different
> groups (parallelism
> assumption). This assumption can be tested in SPSS with a
> special design
> with a factor × covariate interaction. When the parallelism
> assumption is
> not met, it is suggested to ignore the adjusted treatment effects test
> (i.e. the factor of the standard ANCOVA) and to compute and
> report separate
> regression slopes for all groups and/or employing the Johnson-Neyman
> procedure (see e.g., Huitema 1980: 104).
>
> Has anybody written a SPSS syntax program or macro to perform the
> Johnson-Neyman procedure (see e.g., Huitema 1980: 271-)? (It is not
> directly available in SPSS.) Alternatively, does anybody know
> a software
> (preferably freeware) to compute it?
>
> Thanks,
>
> Emili
>
>
> Reference
>
> Huitema, B. E. 1980. The analysis of covariance and
> alternatives. - Wiley,
> New York.
>
>
>
> _______________________________________________________
>
> Emili GARCIA-BERTHOU, Ph.D.
>
> Dept. Ciencies Ambientals   E-mail:   caegb@fc.udg.es
> Universitat de Girona
> E-17071    GIRONA           Tel.:     + 34 972 418 467
> Catalonia, SPAIN            Fax:      + 34 972 418 150
> _______________________________________________________
>