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Hi All, Thank you all for your comments. John your right it is a mixed design as there are different children in the intervention and control conditions. I referred to it as the repeated measures as that is the part of the comparison that I am concerned with, apologies for the confusion. Best, Catherine [http://www.bangor.ac.uk/emailtpl/logo-a2.png]<http://www.bangor.ac.uk/> Catherine Sharp Myfyriwr PhD Seicoleg E-bost: [log in to unmask]<mailto:[log in to unmask]> Ffon: 01248 382735 Ffon symudol: 07984 894 857 Prifysgol Bangor, Bangor, Gwynedd, LL57 2DG [http://www.bangor.ac.uk/emailtpl/twitter-16.png]@prifysgolbangor<https://twitter.com/prifysgolbangor> [http://www.bangor.ac.uk/emailtpl/facebook-16.png] /PrifysgolBangor<https://www.facebook.com/PrifysgolBangor> Catherine Sharp PhD Student Psychology Email: [log in to unmask]<mailto:[log in to unmask]> Phone: 01248 382735 Mobile phone: 07984 894 857 Bangor University, Bangor, Gwynedd, LL57 2DG [http://www.bangor.ac.uk/emailtpl/twitter-16.png]@BangorUni<https://twitter.com/BangorUni> [http://www.bangor.ac.uk/emailtpl/facebook-16.png] /BangorUniversity<https://www.facebook.com/BangorUniversity> From: "Research of postgraduate psychologists." <[log in to unmask]> on behalf of "Baguley, Thomas" <[log in to unmask]> Reply-To: "Baguley, Thomas" <[log in to unmask]> Date: Saturday, 24 September 2016 at 21:10 To: "[log in to unmask]" <[log in to unmask]> Subject: Re: Repeated measures ANCOVA? While common advice, I think this is not correct: "I recently looked into running an ANCOVA myself and found it is inappropriate to use one if the groups significantly differ on your covariate (so baseline score in your case)." One should be cautious about interpreting the treatment effect in sense, but the main reason is that that it suggests that participants weren't randomly assigned to groups (or the randomisation failed). Thus the issue is a problem whether you use ANCOVA or don't use ANCOVA. The advantage of ANCOVA is that if participants only differ because of the scores on the covariate you would in theory be removing the difference caused by the covariate and this makes it superior to the ANOVA whether the randomisation failed or not. If they differ because of other reasons then you may not be able to control for that statistically (but neither will any other analysis you use instead of ANCOVA). The Miller and Chapman paper is wrong (or at least widely misinterpreted). If the argument above holds then it is incorrect to use a regression model or even a partial correlation coefficient in most cases. Jeremy may have a comment (I once suggested we write an update to the Miller and Chapman paper). Thom ________________________________ From: Research of postgraduate psychologists. <[log in to unmask]> on behalf of Amy Atkinson <[log in to unmask]> Sent: 24 September 2016 17:43 To: [log in to unmask] Subject: Re: Repeated measures ANCOVA? Hi Catherine, I think whether an ANCOVA is appropriate would also depend on whether the baseline scores significantly differ between groups (if you have indeed used different participants for your intervention and control conditions, as John suggests). I recently looked into running an ANCOVA myself and found it is inappropriate to use one if the groups significantly differ on your covariate (so baseline score in your case). For more information, see Miller and Chapman (2001), as they explain this in depth, but in an accessible way. Hope this helps, Amy On 24 Sep 2016, at 17:11, Barry, John <[log in to unmask]<mailto:[log in to unmask]>> wrote: Hi Catherine, Forgive me if I am on the wrong track here, but if you have different people in your intervention and control groups, then this is between-groups factor, and you would analyse the data with a mixed (between + within groups) ANCOVA. On the other hand, if all of your participants first do the control condition and then later do the intervention, it is a within-groups (aka repeated measures) design. Hope this helps. Best wishes, John ________________________________ From: Catherine Angharad Sharp <[log in to unmask]<mailto:[log in to unmask]>> Sent: 24 September 2016 08:12:41 To: [log in to unmask]<mailto:[log in to unmask]> Subject: Repeated measures ANCOVA? Good morning everyone, I was wondering if someone would be able to offer some advice. I have been searching into repeated measures ANCOVA with different conclusions being drawn on whether it is appropriate to use the method or not. In my study there are two condition (intervention, control) and three time-points (baseline, post-intervention, follow-up). I need to use baseline scores as a covariate. Is it appropriate to use repeated measures ANCOVA? I have read on forums online that it is not, and that multilevel model should be used, but I am not sure on the reasoning why the ANCOVA method is not suitable. Also, there are peer-reviewed papers published using repeated measures ANCOVA in my research area therefore does that mean it is accepted in the literature. Thank you in advance for your time. Best, Catherine [http://www.bangor.ac.uk/emailtpl/logo-a2.png]<http://www.bangor.ac.uk/> Catherine Sharp Myfyriwr PhD Seicoleg E-bost: [log in to unmask]<mailto:[log in to unmask]> Ffon: 01248 382735 Ffon symudol: 07984 894 857 Prifysgol Bangor, Bangor, Gwynedd, LL57 2DG [http://www.bangor.ac.uk/emailtpl/twitter-16.png]@prifysgolbangor<https://twitter.com/prifysgolbangor> [http://www.bangor.ac.uk/emailtpl/facebook-16.png] /PrifysgolBangor<https://www.facebook.com/PrifysgolBangor> Catherine Sharp PhD Student Psychology Email: [log in to unmask]<mailto:[log in to unmask]> Phone: 01248 382735 Mobile phone: 07984 894 857 Bangor University, Bangor, Gwynedd, LL57 2DG [http://www.bangor.ac.uk/emailtpl/twitter-16.png]@BangorUni<https://twitter.com/BangorUni> [http://www.bangor.ac.uk/emailtpl/facebook-16.png] /BangorUniversity<https://www.facebook.com/BangorUniversity> Rhif Elusen Gofrestredig 1141565 - Registered Charity No. 1141565 Gall y neges e-bost hon, ac unrhyw atodiadau a anfonwyd gyda hi, gynnwys deunydd cyfrinachol ac wedi eu bwriadu i'w defnyddio'n unig gan y sawl y cawsant eu cyfeirio ato (atynt). 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Mae unrhyw farn neu safbwynt yn eiddo i'r sawl a'i hanfonodd yn unig ac nid yw o anghenraid yn cynrychioli barn Prifysgol Bangor. Nid yw Prifysgol Bangor yn gwarantu bod y neges e-bost hon neu unrhyw atodiadau yn rhydd rhag firysau neu 100% yn ddiogel. Oni bai fod hyn wedi ei ddatgan yn uniongyrchol yn nhestun yr e-bost, nid bwriad y neges e-bost hon yw ffurfio contract rhwymol - mae rhestr o lofnodwyr awdurdodedig ar gael o Swyddfa Cyllid Prifysgol Bangor. This email and any attachments may contain confidential material and is solely for the use of the intended recipient(s). If you have received this email in error, please notify the sender immediately and delete this email. If you are not the intended recipient(s), you must not use, retain or disclose any information contained in this email. Any views or opinions are solely those of the sender and do not necessarily represent those of Bangor University. Bangor University does not guarantee that this email or any attachments are free from viruses or 100% secure. Unless expressly stated in the body of the text of the email, this email is not intended to form a binding contract - a list of authorised signatories is available from the Bangor University Finance Office.