Hi All,
I am performing multiple regression with a categorical predictor and a
continuous predictor (continuous outcome variable), and data screening
following Tabachnick & Fidell.
They note that there are differences in data screening for grouped and ungrouped
data. They say that if you are performing multiple regression you are screening
ungrouped data.
But as I have a categorical predictor in my regression (experimental condition),
my data are grouped (?).
So am I right to think that I should screen as for grouped data rather than
ungrouped? (that is, look for outliers, check for normality etc. within each
group separately rather than among all cases at once).
Any advice on this would be great.
Thanks,
Laura
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