Stepwise regression "match"Hello,
I have a stepwise regression and I have the following results when I save the model in the database :
What does that mean ? Indeed, I have several coefficients for the same modality in a variable and it makes me "match". For example the modality "39" has 2 coefficients, "1" and "-1"
What are the "match"?
Thank you for your help
AnalyticsRe: Stepwise regression "match"I'll take a crack at this, but it would help if you attach a snapshot of the data file. It appears that your variable Sem. fab was grouped by JMP into two bins - some of the values were assigned +1 and others -1. I believe the stepwise model will group a nominal variable, according to groups that work "best" in the model, so this variable appears to have been split into two groups. That is fine, if Sem. fab is really a nominal variable (I'm guessing it refers to two designated groups of manufactured parts, for example). Since it has numeric values, I'm not sure - and if it really is a continuous measure, then you should change the data type and model it that way.
Assuming it is a nominal variable, then you model is simply estimating 2 constant values - one for one of the groups and another for the other group. So, your model is predicting the intercept +/- and constant value, depending on which group it is in. This suggests to me that a stepwise regression is not the most useful way to look at this data. I'd suggest doing some more exploratory graphical analysis, since there appear to be 2 groups of observations, each with a predicted value. Are there no other explanatory variables for you to model? With 2 predicted continuous outcomes, and 1 nominal variable (identifying the 2 groups of observations), a simple t test may suffice.
Re: Stepwise regression "match"Here is a sample file I want to make a logistic regression model to predict the "Quality" variable representing the quality of cheeses.
In the example, I only put 6 variables but actually there is much more.
Before making my logistic regression model, I wanted to make a stepwise regression in order to select the best variables to integrate them into my model
However, I don't understand why it separates me into several groups the Variable Year, Month and Week
Indeed, these can not be continuous digital variables, they are in the correct format: ordinal digital
Thanks for your help
