You have three doors: P (prize), E1 (Empty) and E2 (empty again). It’s important to keep track of the difference between E1 and E2. So now we draw up a table of all possible scenarios, and mark it up with the odds of you and monty choosing each option, from which we can calculate the probability for what the third door has inside
|You|Probability|Monty|Probability|Remaining Door|Probability|
|:-|:-|:-|:-|:-|:-|
|P|1/3|E1|1/2|E2|1/6|
|P|1/3|E2|1/2|E1|1/6|
|E1|1/3|E2|1/1|P|1/3|
|E2|1/3|E1|1/1|P|1/3|
There’s four possible scenarios, two of which (with total probability 1/3) are bad, and two of which (total probability 2/3) that are good.
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