Discrete variables in a non linear regression model

In the current version of Minitab, you can create these Indicator Variables (dummy variables as Robert calls them) and then add them to your equation. Be careful because there are some assumptions to the use of these variables…Robert can tell you what they are. Even better, Mini 16 will have these in a new format similar to a general factorial in which you can insert both continuous and discrete variables without the interim step of creating IVs.

Wrong Stan. While a box plot might be interesting to see some visual difference, it is inadequate for drawing conclusions. He asked for influence on his Y. A box plot won’t do this. If he is looking for a significant difference, a box plot won’t do that, a hypothesis test will give him a p value. If he is looking for a prediction model, then regression will do that, not a box plot. The appropriate tool is a function of what he is trying to do and while a graphical approach is a good first step, it is dangerous to draw any definitive conclusions from eyeballing a picture, but you know that. Also, please provide the quote whereby you interpreted my response as a “brag”. Whoops, guess you can’t do that, can ya?

Wrong again. The poster started with “I feel”. Just trying to give him
something better than that.BTW, I can tell you about statistical significance by looking at a box
plot if I know the sample size. You can’t?And yes your plug for 16 was meant to impress, who are you trying to
kid?

Darth,Graphical analysis is way underrated. And yes, after seeing 10’s of
thousands of these things, I know when I am seeing a difference vs “I
feel”.What has happened to your sense of humor?Oh wait, never mind, I know.

  For a categorical variable with three levels you will need to build two dummy variables.  As for Maturity and Staffing – they are yes/no so they can be coded -1,1.
  That takes care of the purely techical and you could, of course, just forge blindly ahead and run a regression and who knows what you will get. However, I’d recommend pausing and thinking about a few other things before proceeding.
  In your first post you said ” I feel this variable has a strong influence on the response variable.” and I chose this to mean that you had actually plotted the data and seen a difference between pricing types.  If, on the other hand, this is a literally statement and you haven’t looked at the data via plotting then you really need to take Stan’s advice and do this.
  As for adding the terms to the model – this goes back to my statement concerning the independence of the X’s.  You can just shove them into a regression package and, if they aren’t perfectly confounded with one another, the machine will spit out a  regression model but it may be of very little value.  Since you are using Minitab you can’t look at condition indicies but it is my understanding that you can look at VIF’s and I also understand that Minitab has the “jitter” option in plotting. 
  What you should do is look at jitterd plots of the X’s against one another to make sure that, at least as far as pairwise comparisons are concerned, they are reasonably independent of one another.  You should then build a model with everything in it and look at the VIF’s.  The VIF’s will at least tell you how any one variable is behaving relative to the others.  If a term has a VIF that is unacceptable (usually a VIF of 10 or greater) you shouldn’t include it in your model building effort.

Don’t you hate it when the parents fight?
Stevo
Ps – Hope the make up sex is good.

How can I get access to MiniTab 16?

Stan’s inputs will be most useful if the fine folks at Minitab are afflicted with excessively positive self-images.

Darth,
Not sure what the agreement is now but it used to be when Minitab asked you to evaluate a future release they normally asked you not to discuss it in such a public format. Has that changed?
Regards

Thanks for the invite Stanny.To which “this” are you referring?

Stan,
Your ongoing personal attacks are getting tiresome. I have given you leeway because of your personal situations but time to either up your dosage or take a break. You are becoming an embarrassment to yourself and others around you. If you really want to continue this I, unlike Johnny, will be more than glad to take on the challenge. I respect your knowledge and experience but you are turning into a real jerk although others may argue with the phrase, “turning into a real jerk”. Get the message from some of the other posts.