 |
 |
You should average the the two runs before doing the group analysis. Best Regards, Donald McLaren, PhD On Thu, Jun 16, 2016 at 2:19 PM, Malak abu shakra <[log in to unmask] > wrote: > Dr. McLaren, > > Please forgive my dwelling on this issue but one last related question: > the same stress test that I used for each alcohol and placebo day contained > two runs. In order to assess the main effect of personality, sex and their > interaction on each of the two rounds under a single condition (alcohol or > placebo), should I also perform two separate full factorial models, one for > each run or is it legit to just do one that combines the two? > > Thank you again for the very clear responses and helpful answers. > > Malak > > > On Wed, Jun 15, 2016 at 7:37 AM, Donald McLaren <[log in to unmask]> > wrote: > >> Yes. >> >> On Jun 15, 2016, at 2:08 AM, Malak abu shakra <[log in to unmask]> >> wrote: >> >> Dear Dr. McLaren, >> >> Thank you ! am I to understand, based on your response, that running a >> full factorial twice, once for alcohol and another placebo would be the >> valid way to go? >> >> Malak >> >> On Mon, Jun 13, 2016 at 1:46 PM, MCLAREN, Donald < >> [log in to unmask]> wrote: >> >>> No. You can't use a full factorial model for looking at the >>> between-subject effects if you have repeated model. What you need to do is >>> to run a model(s) without repeated measures to look at between-subject >>> effects. >>> >>> >>> Best Regards, >>> Donald McLaren, PhD >>> >>> >>> On Mon, Jun 13, 2016 at 12:49 PM, malak abu shakra < >>> [log in to unmask]> wrote: >>> >>>> Dear SPMers, >>>> >>>> I have a quick question re. how much information to model using the >>>> full factorial design: my study included one within-subject factor (2 >>>> levels, alcohol vs placebo conditions) and two between-subject factors >>>> (risk profile: 2 levels; sex, 2 levels). >>>> >>>> I am aware that a flexible factorial should be used to compare >>>> within-subject effects and full factorial for between-subject differences. >>>> What I'm not quite sure of is the following: >>>> >>>> Even though I do not my full factorial model to look at within-subject >>>> differences, would it be statistically preferable that I still feed the >>>> model ALL the information obtained for subjects on both the placebo and >>>> alcohol conditions? (meaning, condition would be added as a third factor in >>>> my full factorial, with non-independent observations and equal variance). >>>> Or, would it alternatively be better if I repeat the same analysis twice, >>>> feeding it the placebo information the first time and alcohol information >>>> the second? >>>> >>>> Thank you very much ! >>>> >>>> >>>> -- >>>> Malak Abu Shakra Doctoral Student >>>> Clinical Psychology >>>> Psychology Dept. Robert O. Pihl Lab >>>> McGill University >>>> 1205 Dr. Penfield Avenue >>>> Stewart Biology Building - Room W8/37 >>>> Montreal, Quebec, H3A 1B1 >>>> Canada >>>> >>>> >>> >> >> >> -- >> Malak Abu Shakra Doctoral Candidate >> Clinical Psychology >> Psychology Dept. Robert O. Pihl Lab >> McGill University >> 1205 Dr. Penfield Avenue >> Stewart Biology Building - Room W8/37 >> Montreal, Quebec, H3A 1B1 >> Canada >> >> "The most erroneous stories are those we think we know best - and >> therefore never scrutinize or question". >> Stephen Jay Gould - >> >> >> > > > -- > Malak Abu Shakra Doctoral Candidate > Clinical Psychology > Psychology Dept. Robert O. Pihl Lab > McGill University > 1205 Dr. Penfield Avenue > Stewart Biology Building - Room W8/37 > Montreal, Quebec, H3A 1B1 > Canada > > "The most erroneous stories are those we think we know best - and > therefore never scrutinize or question". > Stephen Jay Gould - > > >