Poisson Distrbution quickie

statman101 · #1 $Old$ November 4th, 2009, 10:31 AM

When lamba = 5

and you want to know the P(x <= 8)

why is P(x<=8) = F(8;5)

but P(x=8) = F(8;5) - F(7;5)

Im confused, i thought the P(x<=8) would equal
the sum from 0 to 8

and P(x=8) would equal F(8;5)

statmajor · #2 $Old$ November 4th, 2009, 12:27 PM

Quote:

Originally Posted by statman101 $View Post$

When lamba = 5
Im confused, i thought the P(x<=8) would equal
the sum from 0 to 8

and P(x=8) would equal F(8;5)

Both statements are correct.

P(x<=8) =P(x=0) + P(x=1) + P(x=2) + P(x=3) + P(x=4) + P(x=5) + P(x=6) + P(x=7) + P(x=8)