1. Odds vs. Probabilities
Odds ratio in SPSS (Exp(B)) is an odds rather than a probability
Odds = success/failure
Probability = Likelihood of success for any one person

2. Null vs. Specified Model
Null model
Odds Ratio = 26/24 =
Specified Model
Odds Ratio =
(e .549 where e = 2.718)
What are a single person’s odds of passing given a one
unit change in Aptitude?
= Prior odds of passing x increase due to 1 point aptitude
= x =

3. Probability Odds = x/(1-x)
where x = probability of occurrence of event (i.e., passing)
= x/(1-x)
Solve for x, x = .652
Conclusion: A one unit increase in aptitude, increases the probability of being successful from 52% to 65.2%