Having read the explanations people are offering, I think maybe a new
example is needed. Although Statistics was not my favourite of A levels
subjects, I did grasp the concept of simple probabilities (like this)
and we often did examples using playing cards.
e.g. What is the chance of picking a heart from a pack of 52 normal
The answer is 13/52. Say that a heart was selected, then what is the
probability of selecting another heart if thinking independently of the
previous event. The answer would be 12/51, because there are only 12
hearts left, and 51 cards in the pack.
Should this method of working probabilities not suggest that the
remaining doors each have a probability of 1/2 rather than 1/3 and
This is the way I understand it. Have I got the wrong idea, and is this
P.S. Can anyone explain to me how and why this problem is relivant to
the PY104 course???
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