Quote from A_of-s_t
Just so I seem to be justifying myself even though I really don't care:
Let n be the amount of total choices. The probability of picking the right choice is: 1/n
One choice is eliminated:
1/ (n-1)
Here is another:
You are told to either switch or stay, that means you have two choices. Thus, 1/2.
Let n be the amount of total choices. The probability of picking the right choice is: 1/n
One choice is eliminated:
1/ (n-1)
Here is another:
You are told to either switch or stay, that means you have two choices. Thus, 1/2.
the whole practice of calculating probability is to do it at the 'highest level'/first step where things become inconsistent across different scenarios*('point of deviation' - my own term for this activity, do not use in public).(this may or may not be how it is in proper mathematical sense, but its always been the case in my math classes and it works perfectly fine in this scenario). if you don't follow this practice, then you end up calculating the sub-scenarios of a particular scenario(ala, only a PART of ALL scenarios).
so, lets break this down:
1. player picks a door
2. host opens a door to reveal a goat
3. player picks between remaining doors
the fault is that most people will think that 'point of deviation' is at st.3, whereas it is ACTUALLY at st.1. this is because the activity of picking a door is RANDOM.
when you start your calculations on st.3, it is INDEED 1:2 odds, BUT like i said above, you're only calculating a PORTION of ALL possible scenarios, making your calculations invalid.
*maybe a better phrasing is: the FIRST 'step' where randomness comes 'into play' in a given case study.
None.