/sci/ - Science & Math

what's the standard deviation?

It's not given, is there a way to calculate it and is it even necessary for the problem? I'm pretty lost here so your guess is as good as mine.

Looks like Poisson distribution.

So is there like a formula I can use then form knowing its distribution type?

>>3996895
>derp

http://en.wikipedia.org/wiki/Poisson_distribution#The_distribution_equation

Set lambda = 2.5 as it is given in your homework.

>>3996876
erm, there must be more to the question...

every single person could wait 2.5 minutes, and the mean is 2.5.

a) probability someone waits 4 minutes or more is 0
b) probability of customer served in first 2 minutes is 0 (because all served 30 seconds later)
c) THIS JUST IN! WAIT MORE THAN 2:31 AND YOU GET A FREE MEAL! GUARANTEED!
no1 ever ever gets a free meal

"FUCK! if only you guys were one second slower, you got my mother fucking hopes up!" - every single customer, ever.

>>3996901
Part of the assignment is finding a suitable distribution. For example, the exponential distribution

>>3996929
but there isnt enough information! the answer completely changes depending on the value of the SD.
in my example (SD = 0) my answer is correct, changing the SD to anything else changes the answer.

therefore, the question has no single answer, and is bogus, unless you have some extra information to share with us?

That's all the question gives. We're learning integration techniques and such so I'm fairly certain integrals need to be used in solving this question.

>>3996952
and yet the answer is still variable....

>>3996939
There is no reason to assume a standard deviation of 0. They don't have a timer that goes 'beep beep' 2:30 is over, help the customer now.
Most likely, it's exponentially distributed.
In that case, it's easy to answer a,b,c/

>>3996953
'exponentially' distributed? are you sure? i presumed it would be normally distributed, but im still gonna need that SD..


it could be 6 people, served at
2:20
2:23
2:28
2:32
2:37
2:40

answers A and B i gave would still be correct, for C it would change to "any higher than 2:42, and you get a fee meal!"
i mean fuck, theres no information at all other than a mean, you obviously cat math with the number '2.5 minutes' as it stands alone
i mean, fuck! we dont een know how many people attend the restaurant!

>>3996973
>normally distributed
You don't know much do you?
That is the least likely distribution. Seriously.

>>3996989
really? why?
random values equally spaced either side of a mean are the most common for this kind of thing, or so i thought.

>>3997007
Who said they were equally spaced?
All he has is a mean value. That's a classical application for Poisson.

Lord help her she's an atheist~

>>3997021
even so, poisson distribution doesnt mean anything with the mean alone either

>>3997024
lol, i like that song =D

>>3997027
>poisson distribution doesnt mean anything with the mean alone either

Wut?
>implying you need more parameters

>>3997036
wat?
lol, whats the answer to OP's questions then?

>>3997039
Plugging in the values is left to him.
/sci/ is for giving advice, not for doing homework.