Math Question

[SacDuc]

This was also helpful:

http://www.intmath.com/Counting-probability/12_Binomial-probability-distributions.php

When I can't sleep tonight I will set myself to really making sense of that.

sac



/or I'll just punch the clown and go back to sleep

[causeofkaos]

punch the clown 42 times then goto sleep.

[Rameses]

Restate the question:

Let's say some tells you that there is a 9:1 chance that when you start a thread on the DMF some douche bag will threadjack it. Assuming it is possible to start an infinite amount of individual threads, how many threads would you have to start before you could say with 95% certainty that there is (or is not) a 9:1 chance that someone will say something douchey?


sac

Can we lay odds on who it'll be that says something douchey??




(And when did it change from 99% to 90%?)

[GAAN]

This is just the shit I think about when I'm awake at 3am. And no, I wasn't high.

sac

well

then that's your answer

think about it whilst high and then there is your answer

[Speeddog]

~~~SNIP~~~
Is this a valid question:

I ran 100,000 trials and 90,000 came up x and 10,000 came up y. How sure can I be that the ratio of x to y is actually 9:1?

Show you work.

sac

How big is the population that you're sampling from?

Because if it's 100,000, well, you know for sure the ratio is 9:1.
If it's 100,000,000,000,000,000,000,000,000,000 then your sample is not so good.

[SacDuc]

How big is the population that you're sampling from?

Because if it's 100,000, well, you know for sure the ratio is 9:1.
If it's 100,000,000,000,000,000,000,000,000,000 then your sample is not so good.

The number of trials that can be run is infinite. Like flipping a coin. Each flip is an independent trial and there can be infinite number of them. So how many times do I have to flip the coin before I can be 95% sure that the heads to tails ratio is 1:1? Being 100% sure through the use of repeated trials is of course impossible.

sac

[Triple J]

The number of trials that can be run is infinite. Like flipping a coin. Each flip is an independent trial and there can be infinite number of them. So how many times do I have to flip the coin before I can be 95% sure that the heads to tails ratio is 1:1? Being 100% sure through the use of repeated trials is of course impossible.

sac

Easy.

It takes the same number of trials as it does licks to get to the center of a Tootsie Roll Pop.

[mitt]

How did I miss this thread, I do this all the time for predicting pass / fail - I don't have all my notes with me, but let me think about it.

the general eqn is

P = 1-p^n         

p = individual probability of event happening (in your case 1%)
n = number of tests (what you want to know)
P = chance of finding at least one event (in your case you want to find it at least 95% of the time)

[derby]

The number of trials that can be run is infinite. Like flipping a coin. Each flip is an independent trial and there can be infinite number of them. So how many times do I have to flip the coin before I can be 95% sure that the heads to tails ratio is 1:1? Being 100% sure through the use of repeated trials is of course impossible.

sac

http://en.wikipedia.org/wiki/Law_of_large_numbers

[mitt]

So, I am pretty sure your answer is 299 times.

n = ln(.95)/ln(1-.01) = 289.07


mitt

[zooom]

The answer is...... vagina.

or boobies!

[Speedbag]

Yesssssss.

I hear Ducati plans to make a hypermotard.

[SacDuc]

How did I miss this thread, I do this all the time for predicting pass / fail - I don't have all my notes with me, but let me think about it.

the general eqn is

P = 1-p^n         

p = individual probability of event happening (in your case 1%)
n = number of tests (what you want to know)
P = chance of finding at least one event (in your case you want to find it at least 95% of the time)

Cool! Thanks mitt! Now I might actually sleep tonight.

sac


/the rest of you can go to hell!   

[SacDuc]

Yesssssss.

I hear Ducati plans to make a hypermotard.

Did you hear that Bacon Junkie got a 999?

sac



/because he did

[lethe]

Did you hear that Bacon Junkie got a 999?

sac



/because he did

the math just don't add up on that one