# how do I get the intercept in PLUM ordinal regression?

#### miss_t

##### New Member
I am running a ordinal regression model with spss plum. I would like SPSS to print me the intercept, but somehow I can't find the synax command for it. Anyone familiar with the problem?

#### TheAnalysisFactor

##### New Member
It should be there by default, but it's called "Threshold" in the output. There will be multiple intercepts on a PLUM model.

Karen

#### miss_t

##### New Member
thanks a lot. so, you say that we got k-1 intercepts instead of only one?

#### TheAnalysisFactor

##### New Member
Yes. You need those to figure out the predicted probabilities for each outcome category.

Scott Long has a really good book on regression for categorical outcomes, including ordinal regression. You may be able to get it in your library.

I also did a webinar on logistic regression, including ordinal and nominal. It was a while ago, but you can download the recording for free: http://www.theanalysisfactor.com/binary-ordinal-multinomial-logistic/.

Karen

#### miss_t

##### New Member
I see now: probability for highest category or lower=1, so basically just convert and substract thresholds for all the other categories...thanks that was helpful! I had only seen models with 1 constant/intercept so far and got pretty confused.
Btw:i just subscribed to your webinars!

#### TheAnalysisFactor

##### New Member
Yes, if you're trying to compute predicted probabilities for each category, just remember that the equation is giving you cumulative probabilities, so as you surmised, you'll have to subtract.

Also, be careful b/c SPSS uses a strange formula (it makes all betas but the intercept negative). It makes the results more intuitive, but can mess up predicted probabilities if you're not careful.

http://www.theanalysisfactor.com/ordinal-logistic-regression-mystery/

And I look forward to seeing you on the webinars!

Karen