## mariomintchev Group Title 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).) one year ago one year ago

1. mariomintchev Group Title

2. mariomintchev Group Title

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

3. Jemurray3 Group Title

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

4. Jemurray3 Group Title

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

5. mariomintchev Group Title

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

6. mariomintchev Group Title

"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 Group Title

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 Group Title

because you can do 1-the other

9. mariomintchev Group Title

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

10. Jemurray3 Group Title

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

11. mariomintchev Group Title

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

12. phi Group Title

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

13. mariomintchev Group Title

so what i said above ^^^ ???

14. phi Group Title

you left out 0

15. mariomintchev Group Title

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

16. phi Group Title

yes

17. mariomintchev Group Title

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

18. phi Group Title

with lambda= 2.5*8 =20

19. mariomintchev Group Title

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

20. mariomintchev Group Title

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

24. phi Group Title

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

25. mariomintchev Group Title

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