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Random slopes for 2 variables and random intercept for 1 variable

7 messages · Thierry Onkelinx, Shadiya Al Hashmi

#
Good morning,


I have a data design which includes 3 factors of interest/*experimental
manipulations* (using Barr et. al?s (2013) terminology); namely *Listgp*
(listener group: T[monolinguals], TA [bilinguals] and TQ [Turkish speakers
who know Arabic through reading Quran]), *length* (long and short vowels)
and *context (emphatics, pharyngeals, plain and q)*.



*Listgp* is a *between-listener* (subject) and *within-stimulus* (item)
variable [(1|listener), (1+Listgp|stimulus)] while both *length* and
*context* are *within-listener* and *between-stimulus* variables
[(1+length|listener), (1|stimulus) and (1+context|listener), (1|stimulus)].



My question is, how can I code this in the following maximal model lacking
the random effects (for the time being?



maxmodal<- glmer(match ~ Listgp + length + context + gender + age + freq.,
data = msba, family = "binomial", control = glmerControl(optimizer =
"bobyqa"), nAGQ =1)



Here is more information on the variables involved.

*DV/Y (response):* match

*Random effects:* listener and stimulus

*Fixed effects/predictors:* a) *By-listener predictors*+ b) *by-stimulus
predictors: *

*a) By-listener predictors:* (*3*)

*1. Factors: (2)*

-*Listgp* (listener group): effect of interest (T: monolingual Turkish
speakers, TA: bilingual Turkish speakers and TQ: Turkish speakers who know
Arabic through reading Quran).)

-*gender* (female and male)



*2. Continuous predictors (1)*

-*age *(age of listeners at the time of experiment)



*b) By-stimulus predictors: (3)*

*1. Factors: (2)_*

-* context *(stimulus context: emphatic, pharyngeal, plain and q)

-*length *(stimulus length: long and short)

*2. Continuous predictors: (1)*

-*freq*. (stimulus frequency as per arabiCorpus)

Number of obs: 1224, groups:  listener, 51; stimulus, 24





Appreciating your kind input.
#
Dear Shadiya,

glmer() requires at least one random effect. You can use glm() to fit the
model without random effects.

Best regards,

ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature and
Forest
team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance
Kliniekstraat 25
1070 Anderlecht
Belgium

To call in the statistician after the experiment is done may be no more
than asking him to perform a post-mortem examination: he may be able to say
what the experiment died of. ~ Sir Ronald Aylmer Fisher
The plural of anecdote is not data. ~ Roger Brinner
The combination of some data and an aching desire for an answer does not
ensure that a reasonable answer can be extracted from a given body of data.
~ John Tukey

2016-04-27 10:38 GMT+02:00 Shadiya Al Hashmi <saah500 at york.ac.uk>:

  
  
#
Thanks Thierry but I need the random effects in the model since I am
working within a generalized mixed effects model. That's why I used glmer.

The reason why I didn't include the random effects in the model is that I
wasn't sure of how to translate the slopes and intercepts of the variables.

Two ways I could think of, however, are as follows.

maxmodal<- glmer(match ~ Listgp + length + context + gender + age + freq. +
(0-Listgp|listener), (1+length|listener)+(1+context|listener),
(1+Listgp|stimulus), (0-length|stimulus), (0-context|stimulus), data =
msba, family = "binomial", control = glmerControl(optimizer =
"bobyqa"), nAGQ =1)

maxmodal<- glmer(match ~ Listgp + length + context + gender + age + freq. +
(1-Listgp|listener), (1+length|listener)+(1+context|listener),
(1+Listgp|stimulus), (1-length|stimulus), (1-context|stimulus), data =
msba, family = "binomial", control = glmerControl(optimizer =
"bobyqa"), nAGQ =1)


However, I am not sure either is the right way to go about it.

Best wishes,

Shad

On 27 April 2016 at 11:45, Thierry Onkelinx <thierry.onkelinx at inbo.be>
wrote:

  
  
#
Dear Shad,

Your question isn't very clear. You'll need to tell use which random slopes
you want to add to the model.

ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature and
Forest
team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance
Kliniekstraat 25
1070 Anderlecht
Belgium

To call in the statistician after the experiment is done may be no more
than asking him to perform a post-mortem examination: he may be able to say
what the experiment died of. ~ Sir Ronald Aylmer Fisher
The plural of anecdote is not data. ~ Roger Brinner
The combination of some data and an aching desire for an answer does not
ensure that a reasonable answer can be extracted from a given body of data.
~ John Tukey

2016-04-27 11:17 GMT+02:00 Shadiya Al Hashmi <saah500 at york.ac.uk>:

  
  
#
Dear Thierry,

Apologies if my question wasn't clear.

I need to add a slope for Listgp per stimulus, a slope for length per listener and a slope for context per listener. 

Listgp per listener is intercept only, length and context per stimulus per listener are both intercept only.

Hope this clarifies things.

Best wishes,

Shad

Sent from my iPhone

  
  
#
Adding (Listgp|stimulus) + (length + context|listener) to the formula would
add these slopes and their correlations.

Other options are possible. e.g. (0 + Listgp|stimulus) + (0 +
length|listener) + (0 + context |listener). Please have a look at
http://glmm.wikidot.com/faq and look for "Model specification etc." (0 +
x|group) is explained on that webpage.

ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature and
Forest
team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance
Kliniekstraat 25
1070 Anderlecht
Belgium

To call in the statistician after the experiment is done may be no more
than asking him to perform a post-mortem examination: he may be able to say
what the experiment died of. ~ Sir Ronald Aylmer Fisher
The plural of anecdote is not data. ~ Roger Brinner
The combination of some data and an aching desire for an answer does not
ensure that a reasonable answer can be extracted from a given body of data.
~ John Tukey

2016-04-27 11:32 GMT+02:00 Shadiya Al Hashmi <saah500 at york.ac.uk>:

  
  
#
Many thanks indeed Thierry!

I tried both options, one with no variation in the intercept and another
with correlated intercept as in maxmodal1 and maxmodal1.1.
When I compared them using anova, the one with no variation in the
intercept was found to better fit the data.
Data: msba
Models:
maxmodal1: match ~ Listgp + length + context + gender + age + freq. + (0 +
maxmodal1:     Listgp | stimulus) + (0 + length | listener) + (0 + context
|
maxmodal1:     listener)
maxmodal1.1: match ~ Listgp + length + context + gender + age + freq. +
(length +
maxmodal1.1:     context | listener) + (Listgp | stimulus)
            Df    AIC    BIC  logLik deviance  Chisq Chi Df Pr(>Chisq)
maxmodal1   29 1169.5 1317.6 -555.73   1111.5
maxmodal1.1 31 1171.8 1330.2 -554.90   1109.8 1.6631      2     0.4354


My task now is to decide whether I need the one with or without variation
in the intercept!

Thanks again Thierry.

Best wishes,

Shad







On 27 April 2016 at 14:34, Thierry Onkelinx <thierry.onkelinx at inbo.be>
wrote: