Question

I need help with problem 4. I'm supposed to use the Poisson Distribution, but I'm confused because part A says 6 or MORE. (I obviously can't go to infinity, so what do I do? If it was 6 or LESS, I would plug in 6, 5, 4, 3, 2, 1... in for P(x).)

Answer 1

@satellite73 @phi @LoveYou*69 @karatechopper @jim_thompson5910 @Jemurray3 @Hero @AccessDenied

Answer 2

So you could find the probability of five or less, right?

Answer 3

Consider the fact that the only two possible outcomes are that it occurs five or fewer times, or six or more times.

Answer 4

yes, because it's not continuous. it's a discrete number. i have an example like that in my notes.

Answer 5

"Consider the fact that the only two possible outcomes are that it occurs five or fewer times, or six or more times."
Ok, continue...

Answer 6

haha well, that was the main hint... If there are only two possible outcomes, and you calculate the probability for one, then you immediately know the probability of the other, right?

Answer 7

because you can do 1-the other

Answer 8

so should i find plug in 6, 5, 4, 3, 2, 1 into the equation and then subtract that answer from 1??

Answer 9

Good idea. Though probably only from 5 down, if you want to include 6 in "6 or more"

Answer 10

so i should do:
p(5)= e^(-2.5) * 2.5^(5) / 5! + p(4)= e^(-2.5) * 2.5^(4) / 4! + ........

Answer 11

I would calculate the prob of 0,1,2,3,4 or 5 events
then 1 - sum = pr(k≥6)

Answer 12

so what i said above ^^^ ???

Answer 13

you left out 0

Answer 14

yeah and included 6. i needa include 0 and exclude 6. everything else seems good though, right?

Answer 15

yes

Answer 16

ok, and for part b do i plug in 15 through 20 for p(x) and then add them up?

Answer 17

with lambda= 2.5*8 =20

Answer 18

wait, what?
do i place that 20 before e and before the ^ (-x) ??

Answer 19

\[(\lambda) ^ - \lambda x) \

Answer 20

i'm gonna log off but please continue helping (with #s 5-8 on the wkst) everyone!! i'll be back tomorrow to continue this madness. haha

Answer 21

@phi @amistre64
can you clarify what i do with the lambda?

Answer 22

for part b
\[ Pr(k)= \frac{\lambda^k e^{-\lambda}}{k!} \]
λ= 20, the number of events in 8 hours

Answer 23

If I did it right, I got Pr(15 to 20) = 0.4542

Answer 24

ok what formula is that? i thought you said we use the poisson one for #4?