Note: See also Additional Example of a Logistic Plot.
The logistic probability plot illustrates what the logistic model is fitting. At each value on the horizontal axis, the probability scale in the vertical direction is partitioned into probabilities for each response category. The probabilities are measured as the vertical distance between the curves, with the total across all response category probabilities summing to 1.
The points in the logistic plot represent the observations from the data table. The horizontal position of each point is determined by its value of continuous factor. The vertical position of each point is randomly chosen to be between curves that correspond to the value of its response category. This jittering of the points makes it easier to see where the points are most dense, but the vertical position does not correspond to the values on the vertical axis. Because a fixed random seed is used, the vertical positions do not differ across multiple fits of the same model.
You can replace variables in the plot by clicking on a variable in the Columns panel of the associated data table and dragging it onto an axis.