Stephen Brand www.statisticsdoc.com

Helga,

Your design appears to be a Repeated Measures ANOVA, with three levels of the between-subject factor (C+I, I only, No Treatment) and two levels of the within-subject time factor. It would have concerns about letting subjects self-select into the static control group. If you can, you want to start with a group of subjects who are willing to participate in the treatments and randomly assign some to a static control group (perhaps a waiting list control group, if the treatment is something of benefit to the participants). Letting subjects self-select out of the treatments means that the groups do not consist of comparable groups of randomly selected individuals. The inferences that you can draw are weaker: to what extent does the control group differ because of treatment effects or self-selection?

HTH,

Stephen Brand

For personalized and professional consultation in statistics and research design, visit www.statisticsdoc.com

-----Original Message----- From: SPSSX(r) Discussion [mailto:SPSSX-L@LISTSERV.UGA.EDU]On Behalf Of Helga Walz Sent: Friday, November 17, 2006 8:39 PM To: SPSSX-L@LISTSERV.UGA.EDU Subject: your assistance, please

To the experts,

To determine differences between conditions such as the following, what statistical procedure

would be most appropriate -

The 2 conditions for the I.V. are (C+I) and (I only) with pre and post tests. If some subjects who are giving the pretest

decide not to participate in condition 1 or 2, I would like to put them into a static or control group.

Would it be appropriate to use a Repeat Measures Mixed ANOVA procedure?

One I.V. is (C+I) and (I only) and the second I.V. is the time - i.e. from pre to post?

Would the same statistical method be appropriate if I randomly assign the 3 conditions

(C+I) and (I only) and (control/static) conditions to a specific location?

Thank you so much for your assistance,

Helga Walz

Helga S. Walz, Ph.D.

Division of Applied Behavioral Sciences

University of Baltimore

1420 North Charles Street

Baltimore, Maryland 21201

Tel.: 410 837-5279

Fax.:410 837-4059