- Model: Given that you need resuscitation, it is equally likely to be treated by either methods (CPR or CPR+defibrillator).
- : Equally likely to survive with CPR or with CPR + defibrillator.
- : More likely to survive with CPR + defibrillator.
- : # out of survivors who were treated by CPR + defibrillator. Under the model and the null hypothesis we will have that has a Binomial distribution with parameters and . In other words if you sample a survivor, it is equally likely that it was treated by CPR only or by CPR + defibrillator.
- : .

**Remark** What if it is more likely for some reason to be treated by CPR+defibrillator rather than by CPR alone? For example say that at most sport centers patients always ended being treated by CPR + defibrillator. This would be a **big trouble**. We might reject the null hypothesis in favour of when in fact we are really **rejecting the model** (specifically, that it is equally likely to be treated by either CPR or CPR + defibrillator).

2007-05-04