# Thread: Probabilites: A formula for finding one from many.

1. ## Probabilites: A formula for finding one from many.

I have multiple probability values there are only two possible values in each category and only one per observation. See example table below. I need a formula to find what the overall probability would be given all the probabilities. I can do an average probability by adding and divided by 3 but I'm thinking there is a combination formula to do this. I'm would prefer to do this in Excel but I also have SPSS. Thanks!

 Values Probability OBS Gender Race GPA Gender Race GPA Overall Probability of Graduating Student1 M W 3.6 .41 .55 .46 ? Student2 F A 3.5 .51 .49 .51 ?

2. ## Re: Probabilites: A formula for finding one from many.

Overall probability requires more information. Some factors are more important than others. The average of the three probabilities would have little, if any, relevance to the overall probability of the student graduating.