Question

Anyone can help me solve this question? [probability and statistic]

The department received 4 calls every 20 minutes. Based on the time given, find the probability that the department will received not more than 3 calls.

Answer 1

do you know if this is Poison based? or not ...

Answer 2

and is there a table of graph of some sorts with this?

Answer 3

yes i know.. i already try but answer i get dfference from lecturer given..

Answer 4

fill me in on how youve tried to work it, becasue its not ringing any bells for me at the moment

Answer 5

mean = 4/20 = 1/5

Answer 6

\[P(x,u) = \frac{e^{-u}u^x}{x!}\]
correct?

Answer 7

P(0,u)+P(1,u)+P(2,u)+P(3,u)

Answer 8

yes that a formula..then when it is less than 3.. we must get when P(X=0)+P(X=1)+P(X=2) right?

Answer 9

yes, but this is "not more than" 3, so we can have 0,1,2, or 3

Answer 10

then the answer different also.. the answer lectrer was 0.4335..

Answer 11

\[\frac{e^{-.2}.2}{0!}+\frac{e^{-.2}.2}{1!}+\frac{e^{-.2}.2^2}{2!}+\frac{e^{-.2}.2^3}{3!}\]
\[e^{-.2}(1+.2+.02+..00133...)\]
\[e^{-.2}(1.22133...)=.9999431...\]
or have a messed it up someplace?

Answer 12

maybe a cumulative from 0 to 3?

Answer 13

what do u mean?

Answer 14

i have a poisonCDF function on my ti83, i was wondering if it would give something else

but it still gives the .9999431...

Answer 15

oh so that have any other formula or what?

Answer 16

http://stattrek.com/probability-distributions/poisson.aspx

the bottom of the page, example 1, is similar to this problem

Answer 17

may i knowthe question ask not more than 3 right? can u tell me more why u take 3 also?

Answer 18

because 3 is not MORE than 3

Answer 19

ok i think i get it now.. thanks a lot..

Answer 20

0 is not more than 3
1 is not more than 3
2 is not more than 3
3 is not more than 3
4 IS more than 3

Answer 21

i think the setup we did was correct, but we have to determine if the mean we are using is accurate

Answer 22

are we wanting to determine the probabiliy of the rate of x calls in 20 minutes? how do we determine the value of u?

Answer 23

i think the lambda was 4,, bcozthe question ask to find not more than 3 and do not have specific time at there.. but i'm not sure..

Answer 24

hmm, with 4, we do get the .43347...

Answer 25

i spose it was to be interpreted as 4 per 1 time interval ...

Answer 26

i think so.. but thank u for ur helping.. :)

Answer 27

good luck ;)

Answer 28

thanks..u too gud luck..