Questions regarding the Data Library "Larks and Owls"

Comments

• EJ

  May 2023

  Hi Daiichiro,

  I am not sure where I can find this data set in the JASP Data Library -- can you tell me where exactly it is?

  E.J.
• kurokida

  May 2023

  Hi E.J.,

  Thank you for your reply, and sorry for the delay in getting back to you.

  You'll see the demo from

  Open -> Data Library -> 17. Mixed Models.

  I also attach an image file.

  Best regards,

  Daiichiro

  スクリーンショット 2023-05-30 162640.png

  
  
• František

  June 2023

  Hi Daiichiro,

  Thanks for reporting the issue.

  Regarding Q1, the fixed effects estimate summary table shows estimates for the sum coded contrasts -- those are usually not directly interpretable (in comparison to dummy coding) but present a better way of estimating random effect models in the presence of interactions. (I.e. The analysis uses sum contrast encoding for categorical (nominal and ordinal) predictors (R uses dummy encoding by default). This scheme is used for better interpretability of models with interactions. However, the fixed and random effects estimates will differ from those obtained from R with default settings. We advise using the 'Estimated marginal means' section for obtaining mean estimates at individual factor levels. For comparing the mean estimates, use the contrasts option.)

  Regarding Q2, there is indeed an error in the 6th contrast: the 4th row should have been -1. I will fix the issue. You can think about the 7th contrast as a difference between the two simple contrasts, i.e., contrast 3 which represents the effect in the evening chronotype and contrast 1 which represents the effect on the morning chronotype. Since we compute the difference, we keep the coding for contrast 3 and multiply the coding for contrast 1 by (-1).

  Cheers,

  Frantisek
• kurokida

  June 2023 edited June 2023

  Hi Frantisek,

  Thank you very much for your reply. I probably understand what you are saying.

  About the 7 the contrast, should I consider the following?

  A = ChronotypeEvening and TimeOfDayEvening

  B = ChronotypeEvening and TimeOfDayMorning

  C = ChronotypeMorning and TimeOfDayEvening

  D = ChronotypeMorningand TimeOfDayMorning

  Contrast3 = A - B

  Contrast1 = C - D

  Contrast7 = (A - B) - (C - D) = A - B - C + D

  So, A's sign = 1, B's sign = -1, C's sign = -1, D's sign = 1.

  By the way, about the plot, is MWCount predicted/estimated values? Is it not the actual observed values?

  Cheers,

  Daiichiro
• František

  June 2023

  Hi Daiichiro,

  Yes, that's exactly the way how the contrasts are constructed.

  Regarding the plot, the visualized points are the raw data aggregated across the random effects specified in "Background data show" field, e.g., participants in this case.

  Cheers

  Frantisek
• kurokida

  June 2023

  Hi Frantisek,

  Thank you very much for your reply.

  Regarding the plot, do you mean the actual observed MWCount that are shown in the data sheet are plotted? If so, I feel the current explanation is slightly misleading. The values are not estimates, are they?

  To figure out the statistically significant pattern, we create a figure that visualizes mean estimates for the idividual groups in the Plots section.

  Cheers,

  Daiichiro