hlsmith (10-17-2015)
Hi Everyone!
I`ve been really stuck on a biostats question that just doesn`t seem to make sense. The work I have is
Pr(X) = (e^-u) (u^x) / X!
Pr(1) = (2.718^-0.65) (0.65^1) / 1! = 0.339
Pr(0) = (2.718^-0.65) (0.65^0) / 0! = 0.522
Pr(2) = (2.718^-0.65) (0.65^2) / 2! = 0.110
Pr(3) = (2.718^-0.65) (0.65^3) / 3! = 0.048
Pr(>3) = 1 – [(Pr3)+(Pr2)+(Pr1)+(Pr0)] = 1 –
Pr(3) is what is getting me as everytime I do it I get 0.048 but the answer is supposed to be 0.024. I just don`t get why the answer is 0.024 as I used the exact same method to calculate the other Pr(X)`s and got the correct answer but for some reason this one just ins`t right. I checked online at two different sources which said the answer is 0.048 so I don`t think its a miscalculation.
Thanks!
hlsmith (10-17-2015)
A computing error:
I paste it in in google and getPr(3) = (2.718^-0.65) (0.65^3) / 3! = 0.048
(2.718^-0.65) (0.65^3) / 3! =
0.02389608065
and in R
Please note that 3! =6Code:> (2.718^-0.65)*(0.65^3) /factorial(3) [1] 0.02389608 > exp(-0.65)*(0.65^3) /factorial(3) [1] 0.02389447
Opendome (10-18-2015)
If you are not sure about this I suggest you to read more about the definition of factorial (the ! sign) before proceeding in this question. And in general this will be important as you will face it in combinatorics.I was jsut wondering why 3! = 6?
Thanks! That's exactly what I was confused about
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