Maths question...probability

closed

unless you live a very secluded life, probability of finding someone you know is about 100%

Oblivion

The likelihood of finding me on Farcebook is Zero.

JimmyTheWig

This has got nothing to do with demographics.
I believe the "229 friends" means the average number of friends on Facebook someone on Facebook has is 229.

Also, people have ignored the website that the OP directs us to, which gives a (pseudo-) random selection of people on Facebook. At my resolution and browser size it shows me 100 people at any one time.

So the question is...
Pick 100 people at random from a sample of 1.2 billion.
What are the chances of one (or more) of those 100 being on your list of 229 who are all in the 1.2 billion?

JimmyTheWig

Oh, so my answer is 1 in 52 thousand.

WTFH

JimmyTheWig wrote: »

Oh, so my answer is 1 in 52 thousand.

Very true, but again we're into variables such as screen resolution and whether the person has uploaded a picture.

usefulmale

Mankysteve wrote: »

It's not going to be 1/6 while a younger person for instance is going be more likely to have friends on facebook than say a 70 year pensioner and there more lilkly to have to friends on facebook than someone who lives in the third world.

Isn't that's why it's called a probability and not a certainty?

cookie365

No, because people are assuming that just because 1 in 6 of a huge population have some characteristic, then 1 in 6 of any population will have the same characteristic. Mankysteve was pointing out how wrong that is.

Incidentally, what's the probability that a person reading this thread has more than the average number of legs?

WTFH

cookie365 wrote: »

No, because people are assuming that just because 1 in 6 of a huge population have some characteristic, then 1 in 6 of any population will have the same characteristic. Mankysteve was pointing out how wrong that is.

Incidentally, what's the probability that a person reading this thread has more than the average number of legs?

The probability is very high. As for assumptions, the only person making them is you.
Manly just repeated what I had said - there are too many variables, so you either have to account for every single one of them, or you have to use probability to come up with an estimate based on the available data.

JimmyTheWig

cookie365 wrote: »

what's the probability that a person reading this thread has more than the average number of legs?

Very high.

bod1467

cookie365 wrote: »

Incidentally, what's the probability that a person reading this thread has more than the average number of legs?

Very low.

Average number of legs is two (or very nearly approaching two). Very few people will have more than two legs, but a reasonable number may have one or even zero legs.