Hello,

I am attempting to model accuracy in a task that contains multiple trial
types, multiple blocks and many subjects. It is a repeated measure design
because each subject completes 160 trials. My current formula for the
regression is this:

Accuracy ~ TrialType * Block + (1 | subjectNumber)

I am now trying to include a symptom measure in the design. This measure
will be the one continuous value for each subject. So the symptom measure
is nested within subject. What is the syntax for including this symptom
measure in the design. I want to know if the symptom measure contributes to
model fit and if higher values increase or decrease the likelihood of
answering the the trial correctly. I know I cannot do this:
Accuracy ~ TrialType * Block * Symptom + (1 | subjectNumber)
, because symptom is nested within subject but I am not sure what else to
do.

Thanks for the help,

Max Elliott

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