# Help with poisson

#### kontrol

##### New Member
I am not a statistician so please have patience with if i am off track.
I want to predict one of three possible outcomes based on history. for example if a student can score 1,2 or three in an exercise, i want to use poisson to predict the probability that the student will score 1,2 or 3 based on the students history of score in previous exercises.

thank you.

#### Dason

Why do you want to use poisson here? That doesn't seem to be an ideal choice.

#### kontrol

##### New Member
Why do you want to use poisson here? That doesn't seem to be an ideal choice.
i thought that is the ideal choice. what should i use and how?

#### Archidamus

##### Member
Poisson is a distribution the has probability masses at 0,1,2,3.... infinity, where all the masses sum up to 1. What you are looking for, I think, is a prediction model. I would first start with the question of, "does a previous score depend on the current score?" You could build a 3x3 contingency table and do a chi-squared test for independence. If you reject the independence claim, then I would tinker with linear regression to see if I could find out the relationship between one score and the next.

#### hlsmith

##### Less is more. Stay pure. Stay poor.
Well, with the outcome being 1,2,3 - which are integers where 1.5 may be impossible. I would look toward multinomial logistic regression to get probabilities. For more clarification, Poisson regression is typically used for count data or rates. Where your data may be best represented by groups, since many components of linear regression may be an issue, such as bounded confidence intervals.