c********k
发帖数: 200 | 1 set 1 has 20 numbers:
5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95,
100
set 2 is identical to set 1.
randomly select a number from set 1, x1,
and randomly select a number from set 2, x2,
now the question is:
what is the probability of x1+x2=100?
much appreciate! | m**n
发帖数: 384 | 2 P=(19/20)*(1/20)=19/400 ???
【在 c********k 的大作中提到】
: set 1 has 20 numbers:
: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95,
: 100
: set 2 is identical to set 1.
: randomly select a number from set 1, x1,
: and randomly select a number from set 2, x2,
: now the question is:
: what is the probability of x1+x2=100?
: much appreciate!
| a***r
发帖数: 420 | 3 pdf：
f(x1)=1/20, x1=5,10,...,100
f(x2)=1/20, x2=5,10,...,100
x=x1+x2
convolution:
fx(t)=sum_x1 [f(x1)*f(t-x1)]
for t=100,
fx(100)=sum_(x1=5,10,...,95) 1/20*1/20
=19/400
【在 c********k 的大作中提到】
: set 1 has 20 numbers:
: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95,
: 100
: set 2 is identical to set 1.
: randomly select a number from set 1, x1,
: and randomly select a number from set 2, x2,
: now the question is:
: what is the probability of x1+x2=100?
: much appreciate!
| B******5
发帖数: 4676 | 4 难道不就是一个set里面有放回的取两个？
19 / 20^2 = 19 / 400 | t**c
发帖数: 539 | 5 Re
【在 B******5 的大作中提到】
: 难道不就是一个set里面有放回的取两个？
: 19 / 20^2 = 19 / 400
| m*********e
发帖数: 13 | | c********k
发帖数: 200 | 7 R code for this?
thanks,
【在 c********k 的大作中提到】
: set 1 has 20 numbers:
: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95,
: 100
: set 2 is identical to set 1.
: randomly select a number from set 1, x1,
: and randomly select a number from set 2, x2,
: now the question is:
: what is the probability of x1+x2=100?
: much appreciate!
| c********u
发帖数: 1608 | 8 这个公式推广是啥？
【在 B******5 的大作中提到】
: 难道不就是一个set里面有放回的取两个？
: 19 / 20^2 = 19 / 400
|
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