Friedman test formula

Hello everyone,
I am new to R and RStudio and would like to know if I am using the formula for the Friedman test correctly. I am using the stats package and the friedman.test function.

My data are repeated measures of difference scores in reaction times for human subjects on a computer task. Each subject has a specific difference score at each point in time. Hence, I believe I have :

  • A dependent variable : the difference scores (Score.D)
  • An independent variable : the times of measurement (three different points in time)
  • A conditioning or blocking variable : the identity (ID) of the participants in the study

Would you say that is correct ? If it is, then the formula should be :

friedman.test(Score.D ~ Time | ID)

Wouldn't you agree ?

If you want to investigate whether Score.D is affected by whether it is the first, second or third time the measurement is done, then yes, the Friedman test would be one way to do that.

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Yes, that is my goal precisely. Thank you for this confirmation.

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