Anyone good at statistic

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03-09-2009, 12:18 AM
ChedWick

Anyone good at statistic

I have two problems on this h/w assignment I cant seem to figure out. One seems simple but at the same time could be tricky and I know I probably am not doing it right. The other is just screwing me. Any help would be appreciated.

1)If four people are selected at random, find the probability that all four were born in January.

2)It has been reported that 3% of all cars on the highway are traveling at speeds in excess of 70 mph. If the speeds of four random automobiles are measured via radar, what is the probability that at least one car is going over 70 mph?
03-09-2009, 12:21 AM
TheOriginalGrumpySpy

I believe the first one is 20736.
03-09-2009, 12:24 AM
TheOriginalGrumpySpy

And of course the second is 16.

I really hope someone calls me out on this.
03-09-2009, 12:29 AM
sponge

Quote:

Originally Posted by TheOriginalGrumpySpy

I believe the first one is 20736.

Quote:

Originally Posted by TheOriginalGrumpySpy

And of course the second is 16.

I really hope someone calls me out on this.

Everything looks good from this end.
03-09-2009, 12:30 AM
mutton

Quote:

Originally Posted by TheOriginalGrumpySpy

I believe the first one is 20736.

you forgot to divide this by ______

but it's not equally likely that you are born in any given month due to the differences in the numbers of days
03-09-2009, 12:32 AM
mutton

Quote:

Originally Posted by ChedWick

2)It has been reported that 3% of all cars on the highway are traveling at speeds in excess of 70 mph. If the speeds of four random automobiles are measured via radar, what is the probability that at least one car is going over 70 mph?

1 minus the probability that no car is going over 70 mph

in "at least 1" problems, it's a lot easier to consider the complement
03-09-2009, 12:35 AM
TheOriginalGrumpySpy

Quote:

Originally Posted by mutton

you forgot to divide this by ______

Are you missing a number here?
03-09-2009, 12:39 AM
mutton

Quote:

Originally Posted by TheOriginalGrumpySpy

Are you missing a number here?

no, ChedWick is
the way i phrased it is terrible but i'll leave it at that

second rule is probability is always between 0 and 1 inclusive
03-09-2009, 12:41 AM
sponge

wait I thought we were fucking with him
03-09-2009, 12:43 AM
mutton

i fuck with people by hinting at the solution in the most tedious ways

and then they thank me for it
03-09-2009, 06:24 PM
Cryptic

Quote:

Originally Posted by TheOriginalGrumpySpy

I believe the first one is 20736.

Quote:

Originally Posted by TheOriginalGrumpySpy

And of course the second is 16.

I really hope someone calls me out on this.

I'm calling you out. I don't know the answer, but I do know that probablities are given in fraction, percentage or decimal form.

For example, the chances of getting tails when flipping a coin is 50%, 0.5, or 1/2. A "probability" of 16 doesn't give any information.
03-09-2009, 06:26 PM
TheOriginalGrumpySpy

You

Are

Daft.
03-09-2009, 06:31 PM
Nermy2k

For the first one there's a 1/4 chance the person is born on a leap year and a 3/4 chance he/she is not.

So your probability of all of them being born in january is:
((1/4)*(31/366)+(3/4)*(31/365))^4

or something
03-09-2009, 06:47 PM
coqauvin

guys fuck math make music and read/write words

it is good for your soul
03-09-2009, 06:50 PM
Nermy2k

Music is pretty much just physics which is just math.
03-09-2009, 06:52 PM
TheOriginalGrumpySpy

I could make music using Fourier Transforms.
03-09-2009, 06:52 PM
coqauvin

well yes but that is beside the point
03-09-2009, 08:30 PM
Sion

Quote:

Originally Posted by mutton

but it's not equally likely that you are born in any given month due to the differences in the numbers of days

which is only relevant if they ask which month.
03-09-2009, 08:32 PM
Cryptic

Hey TOGS, nice of you to jump on the neg rep bandwagon too. Go fuck yourself you pinheaded prick.

Point of fact, if I or anyone else had EVER put down "16" or any other whole number flapping in the breeze as an answer to a PROBABILITY question on a test at an actual accredited school, it would be wrong since that's just NOT how probabilities work.
03-09-2009, 09:06 PM
Mr. E

Cryptic you need to calm the fuck down and quit being a douche. Of course, I don't know if that is possible.

Now, I do hate to agree with Cryptic on anything, but he is right on this one. Nermy's equation for solving the first probability is correct.

The second one is trickier. The odds of one of the four going over 70 is about 2.738%, but I don't remember off the top of my head how to re-figure it for the terms of 'at least one'.
03-09-2009, 09:31 PM
Tekk

Its been a while since statistics, but lets see how much I remember...

These are independent trials, so you can solve them as binomials.

p(x) = [n!/x!(n-x)!]p^x(1-p)^(n-x)

So figure:
sample size n= 4
probability p= 1/12
number of successes x=4

So plug it in to the equation:

[4!/4!(4-4)!](1/12)^4(1-1/12)^(4-4) =

p(x)= .000048 or 1/20736

TOGS was right.

The second one can be solved the same way but instead figure:

n= 4
p= 3%
x= 0

The reason x=0 is because you want at least 1 car. Its easier to just subtract p(0) from 1, then figure out p(1), p(2), p(3), and p(4)

So:

p(0)= [4!/0!(4-0)!](.03)^0(1-.03)^(4-0)

p(0) = .885293

1-p(0) = .114707 or 11.47%

Hope that helps.

Damn I'm bored on a Monday night...
03-09-2009, 09:40 PM
Malicious Intent

fuqq math
03-09-2009, 09:41 PM
Mr. E

Oh damn you are right, I over-complicated the second one.

However, on the first one Tekk you ignored the fact that not all of the months are the same length. Nermy's way was right.
03-09-2009, 09:42 PM
mutton

Quote:

Originally Posted by Cryptic

Hey TOGS, nice of you to jump on the neg rep bandwagon too. Go fuck yourself you pinheaded prick.

Point of fact, if I or anyone else had EVER put down "16" or any other whole number flapping in the breeze as an answer to a PROBABILITY question on a test at an actual accredited school, it would be wrong since that's just NOT how probabilities work.

learn 2 read

Quote:

Originally Posted by Tekk

p(x) = [n!/x!(n-x)!]p^x(1-p)^(n-x)

while this works it's like a rube goldberg machine in this context
common sense gets to the answers a lot quicker
03-09-2009, 09:45 PM
Mr. E

lol, mutton did answer them all right, I should have read the thread
03-09-2009, 09:47 PM
Tekk

Without the sheep avatar, I didn't even know it was mutton posting.
03-09-2009, 10:05 PM
TheOriginalGrumpySpy

Quote:

Originally Posted by Cryptic

Hey TOGS, nice of you to jump on the neg rep bandwagon too. Go fuck yourself you pinheaded prick.

Point of fact, if I or anyone else had EVER put down "16" or any other whole number flapping in the breeze as an answer to a PROBABILITY question on a test at an actual accredited school, it would be wrong since that's just NOT how probabilities work.

But I didn't negarep you :(
03-09-2009, 10:24 PM
benzss

cryptic called somebody else a pinhead.
03-09-2009, 11:00 PM
Pepsi

Quote:

Originally Posted by Cryptic

Hey TOGS, nice of you to jump on the neg rep bandwagon too. Go fuck yourself you pinheaded prick.

Point of fact, if I or anyone else had EVER put down "16" or any other whole number flapping in the breeze as an answer to a PROBABILITY question on a test at an actual accredited school, it would be wrong since that's just NOT how probabilities work.

You know, it's whining like this that makes be want to drag you down to the banning level of reputation.
03-10-2009, 06:09 AM
coqauvin

Quote:

Originally Posted by Pepsi

You know, it's whining like this that makes be want to drag you down to the banning level of reputation.

Next time, Cryptic, BANG, ZOOM, TO THE MOON!
03-10-2009, 10:43 AM
Pepsi

Quote:

Originally Posted by coqauvin

Next time, Cryptic, BANG, ZOOM, TO THE MOON!

Oh hey! The Honeymooners!

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