Math: Conditional Probability

http://www.philipbrocoum.com/?page_id=91

Using O.J. Simpson as an example, I introduce conditional probability.

Category:

Education

Tags:

• math
• conditional
• probability
• O.J.
• Simpson

[PatMurph245]

99% of trolls here are cynical arseholes 100% of the time.

[Stedwick]

@PatMurph245 Ha ha, true that.

[GaijinNH]

This seems like nonsense...HIV isn't random. The percentage of people who have any STD is relatively low, but the percentage of gay men who have an STD is over 90%. If you're gay, and you have a positive HIV test, your chance of actually having HIV is much higher than 9%. The circumstances of each individual change the odds. You can't apply the laws of probability so haphazardly.

[Stedwick]

@GaijinNH First, lovely to have a racist here with us (if 90% of gay people had aids they would all be dropping like flies, lol), and second, yes, OBVIOUSLY if you have more information you can improve upon statistics. It's like if I said that any individual person has a 1% chance of dying this year and you said NO THAT'S WRONG because for somebody who's 95 years old their chance of dying is way higher, therefore you can't apply probability.

[Pantlessness]

I feel like there's a fallacy in using population stats to reflect on a specific individual. That is, the probability of actual infection from, YOU testing positive for AIDS one time, and any randomly selected positive-tester from the population of 100000, is different.

What if you were the ONLY person to take the test? How could it still be 9%.

[Stedwick]

@Pantlessness That's like saying that probability goes out the window if you only play one hand of blackjack at a casino. Not at all. The probability is always the same regardless of how many hands you play. The house always has the upper hand.

[ruslanio]

O.J. Simpson disliked this video.

[misium]

This explanation is really impressive. You are a great lecturer!

[linkchibi]

what ? if people with HIV is 1% of 100,000 it must be 1,000 people with HIV not 100 people

[CrowTitanium]

@CMFangirl I was simply making a point, which some people apparently can't see due to personal issues. I used CDC figures, which seem extreme to me but are accurate.

[CMFangirl]

@GaijinNH a) We weren't given that information. You have no method with which to apply that statistic (which sounds really unlikely, personally).

b)It was a math demo, for christ's sake. He didn't post the video to help you figure out whether or not you have AIDS.

[Ingeniumed]

Conditional probability is hell of a lot better now...thankx!

[MuikJuaggre]

15 people have HIV

[MintedCoin]

wow..thanks so much. i couldnt really understand the khanacademy one on probability but this is amazing!!! i cant thank you enough! thanks for dumbing it down for me, it makes sense now!

[RedStateRoy]

@Stedwick Gay isn't a race. Perhaps "Homophobe" would be more accurate. But good job on the math. Cheers.