[R] (g)lm ordinal or scaled values?
Knut Krueger
Knut-krueger at einthal.de
Mon May 8 16:35:34 CEST 2006
There is a difference in the p- value from 0.000 and 0.012 when I am
using SPSS.
0.000 when I am using the independent variable as scaled 0.012 if I am
using the variable as ordinal.
The independent variable is ordinal but it seems that R is using the
variable as an scaled, because the P- Value is computed with 4.66e-06
so I am not sure which description I am misunderstanding:
SPSS;:
Covariates. Scale predictors <javascript:popup(N2C5F1_term,N2C5F1_def);>
should be selected as covariates
<javascript:popup(N2B079_term,N2B079_def);> in the model. Within
combinations of factor levels (or cells
<javascript:popup(N2AE3F_term,N2AE3F_def);>), values of covariates are
assumed to be linearly correlated with values of the dependent variables.
(A variable can be treated as scale when its values represent ordered
categories with a meaningful metric, so that distance comparisons
between values are appropriate. Examples of scale variables include age
in years and income in thousands of dollars.)
Factors. Categorical <javascript:popup(N2AD73_term,N2AD73_def);>
predictors should be selected as factors
<javascript:popup(N2B481_term,N2B481_def);> in the model. Each level
<javascript:popup(N2B937_term,N2B937_def);> of a factor can have a
different linear effect on the value of the dependent variable.(A
variable with a discrete number of values; an ordinal or nominal
variable. Categorical variables are often used as grouping variables or
factors.)
The data : http://biostatistic.de/temp/testr.csv
lm.data<-lm( dependent ~ var2,family = gaussian)
I don't know whether anybody could explain me the difference between
SPSS and R results but if there are different results then one of them
is wrong :-(
And I do not know which of them.
I hope I explained the problem understandable
Regards Knut
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