Ralitt
2012-Oct-17 19:25 UTC
[R] Please help a struggling student with data set-up for lmer crossed random effects
Hi all, I am just starting my first models in R and am having trouble with some of the basics. The main things at the moment are about setting up my data correctly. I have a repeated measures design-all participants complete 4 experimental conditions. I want to fit a linear mixed effects model with crossed random effects for subject and item. I have 4 conditions, 6 items per condition. Because each condition uses different items, there are 24 total items. Each group of 6 items only occurs in 1 condition, and it occurs in the same condition for all participants. I am interested in including item as a random effect in my model. My question is about labelling the items correctly-should I label them 1-24, or 1-6 for each condition? I'm afraid if I label 1-6 for each condition it will think item 1 was the same item and was repeated in each of the four conditions. But if I label it 1-24 it will look as though 18 of the items are missing in each condition as 6 can only occur in any one condition. So, should I have my data like this: subject item condition 1 1 1 1 2 1 1 3 1 1 4 1 1 5 1 1 6 1 1 1 2 1 2 2 1 3 2 1 4 2 1 5 2 1 6 2 1 1 3 1 2 3 1 3 3 1 4 3 1 5 3 1 6 3 1 1 4 1 2 4 1 3 4 1 4 4 1 5 4 1 6 4 or like this: subject item condition 1 1 1 1 2 1 1 3 1 1 4 1 1 5 1 1 6 1 1 7 2 1 8 2 1 9 2 1 10 2 1 11 2 1 12 2 1 13 3 1 14 3 1 15 3 1 16 3 1 17 3 1 18 3 1 19 4 1 20 4 1 21 4 1 22 4 1 23 4 1 24 4 Sorry for the basic question, but I can't seem to figure this out! -- View this message in context: http://r.789695.n4.nabble.com/Please-help-a-struggling-student-with-data-set-up-for-lmer-crossed-random-effects-tp4646501.html Sent from the R help mailing list archive at Nabble.com.
Ista Zahn
2012-Oct-17 20:47 UTC
[R] Please help a struggling student with data set-up for lmer crossed random effects
Hi, On Wed, Oct 17, 2012 at 3:25 PM, Ralitt <Ralitt at gmail.com> wrote:> Hi all, > I am just starting my first models in R and am having trouble with some of > the basics. > > The main things at the moment are about setting up my data correctly. I > have a repeated measures design-all participants complete 4 experimental > conditions. I want to fit a linear mixed effects model with crossed random > effects for subject and item. I have 4 conditions, 6 items per condition. > Because each condition uses different items, there are 24 total items. Each > group of 6 items only occurs in 1 condition, and it occurs in the same > condition for all participants. I am interested in including item as a > random effect in my model. My question is about labelling the items > correctly-should I label them 1-24, or 1-6 for each condition? I'm afraid if > I label 1-6 for each condition it will think item 1 was the same item and > was repeated in each of the four conditions. But if I label it 1-24 it will > look as though 18 of the items are missing in each condition as 6 can only > occur in any one condition.Well, if I understand correctly that actually is the case (that 18 items are "missing" in each condition") So, should I have my data like this:> subject item condition > 1 1 1 > 1 2 1 > 1 3 1 > 1 4 1 > 1 5 1 > 1 6 1 > 1 1 2 > 1 2 2 > 1 3 2 > 1 4 2 > 1 5 2 > 1 6 2 > 1 1 3 > 1 2 3 > 1 3 3 > 1 4 3 > 1 5 3 > 1 6 3 > 1 1 4 > 1 2 4 > 1 3 4 > 1 4 4 > 1 5 4 > 1 6 4 > > or like this: > > subject item condition > 1 1 1 > 1 2 1 > 1 3 1 > 1 4 1 > 1 5 1 > 1 6 1 > 1 7 2 > 1 8 2 > 1 9 2 > 1 10 2 > 1 11 2 > 1 12 2 > 1 13 3 > 1 14 3 > 1 15 3 > 1 16 3 > 1 17 3 > 1 18 3 > 1 19 4 > 1 20 4 > 1 21 4 > 1 22 4 > 1 23 4 > 1 24 4The second way. Best, Ista> Sorry for the basic question, but I can't seem to figure this out! > > > > -- > View this message in context: http://r.789695.n4.nabble.com/Please-help-a-struggling-student-with-data-set-up-for-lmer-crossed-random-effects-tp4646501.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code.