The Student Room Group

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(edited 2 months ago)
Reply 1
Original post by username17263528
https://isaacphysics.org/questions/poisson_radioactivity?stage=a_level
I’m just wondering for parts c and e of this question how an expected value can be calculated that is different from the mean value. Thank you in advance.

For c) the expected number is different as its really no longer a poisson distribution as the meter reads 5 whenever the counts are 6,7,... so the expected value will be a bit less than the mean.

Not checked e) but I presume its the same
(edited 2 months ago)
Reply 2
Original post by username17263528
Ok, thanks for this. Would you be able to give me a hint on how I could go about calculating the expected value?

A naive way would be to simply use the expected value formula from 0 to 5 with the poisson probabilities then add the 5*P(#>5) at the end.

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