## mariomintchev 2 years ago 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).)

1. mariomintchev

2. mariomintchev

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

3. Jemurray3

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

4. Jemurray3

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

5. mariomintchev

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

6. mariomintchev

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

7. Jemurray3

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?

8. mariomintchev

because you can do 1-the other

9. mariomintchev

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

10. Jemurray3

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

11. mariomintchev

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

12. phi

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

13. mariomintchev

so what i said above ^^^ ???

14. phi

you left out 0

15. mariomintchev

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

16. phi

yes

17. mariomintchev

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

18. phi

with lambda= 2.5*8 =20

19. mariomintchev

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

20. mariomintchev

$(\lambda) ^ - \lambda x) \ 21. mariomintchev 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 22. mariomintchev @phi @amistre64 can you clarify what i do with the lambda? 23. phi for part b \[ Pr(k)= \frac{\lambda^k e^{-\lambda}}{k!}$ λ= 20, the number of events in 8 hours

24. phi

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

25. mariomintchev

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