shows a scatter-plot of these mock data, relating recovery to hours of treatment per week. Although not particularly interesting in itself, this figure serves to highlight a number of important issues regarding why logistic regression is to be preferred in these contexts over other regression procedures.
There are a number of things to note immediately based on an inspection of these data.
The first is that the outcome chosen for analysis in this example can only take one of two values(0 = not recovered and 1 = recovered), any regression technique that has the possibility of predicting any other value is clearly inappropriate for such data (it should be noted that it is not always the case that the outcome has to be divided into two categories, sometimes the outcome will be a continuous variable; whether to actually divide this into two will depend on
the design chosen) secondly, the relationship between the predictor (hours per week) and outcome (recovery) cannot be termed linear, but are best described by an S-shaped (‘sigmoidal’) curve; and thirdly, the variance in the outcomes (recovery) is much smaller at the extreme values of the predictor (intervention time per week) than it is at the central values.
shows a scatter-plot of these mock data, relating recovery to hours of treatment per week. Although not particularly interesting in itself, this figure serves to highlight a number of important issues regarding why logistic regression is to be preferred in these contexts over other regression procedures. There are a number of things to note immediately based on an inspection of these data. The first is that the outcome chosen for analysis in this example can only take one of two values(0 = not recovered and 1 = recovered), any regression technique that has the possibility of predicting any other value is clearly inappropriate for such data (it should be noted that it is not always the case that the outcome has to be divided into two categories, sometimes the outcome will be a continuous variable; whether to actually divide this into two will depend onthe design chosen) secondly, the relationship between the predictor (hours per week) and outcome (recovery) cannot be termed linear, but are best described by an S-shaped (‘sigmoidal’) curve; and thirdly, the variance in the outcomes (recovery) is much smaller at the extreme values of the predictor (intervention time per week) than it is at the central values.
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