First hints for Phoenix [General Sta­tis­tics]

posted by Helmut Homepage – Vienna, Austria, 2014-02-20 20:11  – Posting: # 12465
Views: 15,089

Hi Lucas,

» This is how it would look like according to them: […]

Interesting! I didn’t count, but ~200 subjects is not common in BE studies. It will not look that nice in the real world. The x-axis of the first plot is strange (negative means – I beg your pardon?). The distribution doesn’t look normal but skewed to the left* and the Q-Q plot looks extremely ugly. That’s actually a great example which EDA would suggest to use another trans­formation (e.g., ℯx or xn, where n>1).
However, let’s see what you can get in PHX (I numbered the panels in your plot):
  1. Plotting > XY-Plot (though for the abscissa I would either use the subject’s ID or the pre­dicted model values).
  2. Plotting > Histogram Show relative Frequency. In the current version (6.3) it is not possible to overlay a normal distribution, maybe in the next release?
  3. Plotting > QQ Plot.
  4. Upper part = trivial. Lower part = strange. In PHX the line in the Q-Q plot is fitted auto­ma­tic­ally – I don’t think it is possible to extract the parameters and AIC, BIC.
    BTW, these values are only useful in comparing different models. I cannot imagine what might its purpose here. AICC is the AIC corrected for small sample sizes. It proves that the statis­ti­ci­an is a “push-the-button-type” who does not know what he is doing. Of course you could fit the standard quantiles vs. stud. resid’s by PHX’ linear model.
If the sponsor insists on a similar layout, you have to leave PHX because different types of plots arranged in an array (aka trelis/lattice plots) are not supported. Either export relevant data from PHX and continue the analysis in R or generate the plots in PHX and paste them into a 4-cell table in your preferred text-processor.



Cheers,
Helmut Schütz
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