Probability (part 2)

[WeGotBeatz]

I have been learning probability for over a week now in my statistics class. After every class i was extremely confused. After watching the probability videos in a matter of 1hr it all makes sense. You're amazing at teaching keep up the good work bro i appreciate it.

[iWriteUinMyDeathNote]

HE SAID HELL!!! OH MY FUCKING GOD HE SAID "HELL"

[Stickytaks]

I really liked the example in the end lol ;) 

[Wbjpen]

Coinception.

[niconikko]

SO, there's a (1/2)^100 chance to have 100 heads in a row. Wow, much harder than a lottery ticket !!! LOL

[dingusding]

Please don't use someone else's work to preach your beliefs (islam/atheism/etc).

From About Khan Academy:

If you believe in trying to make the best of the finite number of years we have on this planet (while not making it any worse for anyone else), think that pride and self-righteousness are the cause of most conflict and negativity, and are humbled by the vastness and mystery of the Universe, then I'm the same religion as you.

[tankstocks]

Mutually exclusive events and Independent events do not have same meaning, here Mr khan is talking about Independent events, not mutually exclusive events. Here, Mr, Khan is talking about Independent events.

[MegaTouchReviewer]

sal my atheist brother :).

[DeathG4n]

@MegaTouchReviewer nope, he's a Muslim, and he encompasses very important principles of Islam, which is not being materialistic (he could earn a lot with his harvard degree if he wanted too) and choosing to help people without compensation while remaining humble. truly a great man and an example that people should view as a real muslim instead of the stereotypical violent man with the beard (which is really a minority). I hope more people like sal show the world what islam is really about

[lulu4425]

at 7:53 did he sya" lets switch colors just 4 the hell of it?"

[theindianguy009]

that U sign denotes union ... ryt???? ... i tik i learned dat b4

[theindianguy009]

7 ppl r dumb enuf not to understand dis !!!

[funnyb0y3000]

what program do you use for this?

[ubentu]

@funnyb0y3000 Hey Just used paint, a digitizer tablet, and Microsoft paint... and a screen capture program.

[roarmaster2]

can u please do a video on bearings

[coolslaya]

just wondering, which 7 idiots disliked this?

[catbe123]

good job..



[Megawhites2]

I'm not asking this to be rude or anything but...just out of curiosity, was 5:34 a moment for gas to pass? For some reason that question just keeps nagging me xP

Other than that, thanks for the vid dude. Every time I'm stuck with math, I always turn to youtube and khanacademy saves the day. Thanks for all the time you've given to teach us. It's greatly appreciated.

[paulceltics]

@Megawhites2 wtf??

[TheD3fu53r]

not to be a smart ass or bashing Sal,

but the heads side on a coin is heavier than the tails side, so isnt there more of a chance of it being heads?

[enter08com]

@TheD3fu53r He said in the first video: "EQUALY PROBABLE".

And if we take the conditions you said, than the proportion of H:T wouldn't be anymore 50:50.

I.E. If the heads side is twice heavier, than it'll be 75:25 H:T.

[longhorn4500]

What is the reason for MULTIPLYING 1/2 by 1/2? Why don't we add or subtract or divide? It would be better to explain that.

[bordenw]

jonjonjon1370. Whenever you flip a coin, you have a 50% chance of getting a heads or a tails. Without performing the experiment, this is the data going in. However, it does not always obey this properity. It could depend on the way it's flipped, the side of the coin that is facing up and whether you fiip in onto the back of your hand. You have to have an assumption in order to perform an experiment.

macanudooo, the correct answer is 1/32.

[jonjonjon1370]

Hey Sal, at 3:25, what if I don't get 25 heads out of those 50. Through typing, it's hard to show what I mean. Is that like, the estimation?

[TheKaylaCakesz]

i believe i'm gonna pass my maths test tomorrow :) after this. whooo hooo

[doritoface123]

THUHT

[TheHeytheregirl]

Great videos. May God bless you and your family

[TheHeytheregirl]

Great videos..May god bless you and your family with all the good things

[gennkill]

your videos rock

[cyw0403]

Sal, thanks for the great video as usual, but I would like to correct something. You seem to use "mutually exclusive" and "independent" interchangeably, but concept of mutually exclusive and that of independent are different. We can multiply possible outcomes of each trial not because they are "mutually exclusive," but because they are "independent." Mutually exclusive event let us know that if A happened, B didn't happen while indenpendent even doesn't let us know what happened to B.

[erdwe45]

The probability that Sal is the best teacher in the world iiis....let me see.... 1/1 = 100% !!! =D

[frankthetank1285]

Your videos are excellent and have proved invaluable during my return to college. Thanks!

[91jgphonecall]

i got it!

[youtubalisation]

What do u mean likelyhood or probability? Do you mean if I flip a coin 10 times, i get heads 5 times? In fact, I tried out. I get heads 3 times. What does that mean? Why are we learning this? What is the point?

[youtubalisation]

you are very long-winded......ur videos are getting longer and longer...

[crispybacon100]

it would suck not to get any heads

[Luca220392]

something magical going on in their life : D

[naughtydevil02]

thank you so much i was struggling with this so much i mean i m generally really good at math but i had no background of probability and this is so gr8 thanks:D

[rlexperiment]

What is the probability that in 100 tries, I get 50 heads?

[hmdlamin93]

nice video man! u explain rly well.

[yujisamadesu]

the last sentence may be quite wrong as if it was a person in vegas who had the lucky streak... i thought the part where he said " u get 200 tries (or something...) " should be wrong as it`s a totally different person getting the tries and so the probability should be reduced back to the 50% chance...

[knighttango]

its a very nice leture...

once u get this u can travel any further into probability theory..

[malgrif091]

i'm confused as to why multiplying probabilities in the probability tree will result in the overall probability of the event...Why are you multiplying in the first place?

[knighttango]

after the first event u have half a chance for H...

after the second event u have half the chance of the half we got earler...

half of half is 1/4 and we obtain by multiplication...

[74dorset]

At 6:31 I am confused. ''The probability of getting a heads a second time is completely independent as to whether I got a heads the first time''.

''The more you do it then the probability of getting a heads does increase''.

Can anyone shed some light on this?

[thelemur]

The 2 fysical sepparate actions, of throwing a coin, and it turning out to be a head or tail, 2 times in a row, are completely independant of eachother, obviously. And so, also is the outcome.

BUT, as you keep doing this, the PROBABILITY of the turnout, vill converge to 50/50 % outcome. Thats the point. you CANT ultimately PREDICT anything, but, you can come up with a pretty good GUESStimate, from this theory.

[LoneRiver1]

@74dorset

The key here is that each independent flip is 50% heads. Every time you flip a coin, there's a 50% chance of getting heads, regardless of how the other flips went.

However, when you take multiple flips into consideration, things change. What are the odds of getting X-many heads in a row? As Sal showed, it's 50% times 50% and so on. The odds of a streak continuing get lower and lower as the streak gets longer. This is because you're taking into consideration all the flips beforehand.

[Pr0x1mo]

Khan, have you seen Derren Browns The System video? If you haven't, you would watch all of Derren Browns stuff, he exposes a lot of erroneous beliefs humans have when it comes to probability (how we attribute magical or superstitious beliefs to chance and probability).

[eatmybreads22]

lol, "that probably confused you... and i probably shouldn't have said it." sal is the man.

[xSerbianGirl19x]

Thank you for doing this... Thanks to you i aced my test!!!!

[imalylime]

hahaha youre funny. i wish you were my prof.

[BerserkerEos]

if he was my prof i would love to be a mathimaticien ,,,,,,,,,,, but helas i had a hard time in my school with nasty teachers :(

[oldarney]

BTW you have a scientific calculator view on that windows XP calculator (it can handle exponents).

[yongchunkungfu]

actually for coin flipping.. there's a super slim chance..(but still a chance) that it might not be heads or tails and balance on the rim. HAHA then there should be a certain percentage for that and not work on the coin flipping probability on 100%. But that's just assumed as 0% chance of that anyway.

[robertwc82]

thats true i guess in reality its a 49.9999999999999999999999

999999999999999999999999

999999999999999999999999

9999999999999999999999999

99999999999999999999999999

99999999999999999999999999

99999999999999999999999% chance of getting heads or tails lol

[imbdeepblu]

you set boundries for your experiment. So acceptable outcomes is H or T. If we include what you are talking about then that would be a field. In which we would include a null set

[starlost1957]

Formulas do work when you fiqure it out on everything in this universe!!!

[Budisawsome]

figure*

[MFJVIDEO]

so how accurate is probability? and how the hell do you find that out?

[tbilisidavid]

nice videos

[akabyl]

спасибо большое, хорошее видео, а Вы сами применяете его? Thank you, this is good video, could you apply this probability in casino, lottery or playing automats?

[2cabs2toucan]

The best you can hope for using probability is to calculate least risk bets. The most important thing to learn from calculating probabilities for casino games is that the house wins in the long term. You could learn to count cards at blackjack. It would be interesting to see how much your odds are improved with the casinos multiple decks. Still, they ask good counters to leave the table apparently.

[john656656]

hahaha! had the same mindset when i was doing acturial study at uni. let me explain it to you. People who owns casino has already done their homework, the odds are against you 100%. As to lottery, i will give you an easy example. suppose you buy a 4-number(0 to 9) lottery, the chance you hit the jackpot is 1 in 10*10*10*10(there are 10 digits between 0 to 9), which is 1 in 10000 chance. So forget about winning lotto. work hard and invest, this is the only way.

[sunshinex1104]

i dont understand why you got boo-ed lol .. .

wat you just said was right..

[tdrawdy2]

I really find your videos useful and well-explained. You enunciate clearly and your writing (on whatever program that is) is visible. Thank you.

[Pinepelt]

@tdrawdy2 For all those that are wondering, he's using Microsoft Paint (MS Paint). That's what he made his first videos with, and what this is made with as well.

[calvinhobbesliker2]

technically, the side that a coin lands on is determined by how hard you toss/flip it, which side it sharts on, how fast it spins, air resistance, gravity, etc.

[gatoraid01]

If you assume that you do not know what side is upright when you flip it ...technically all that does not matter. That is if the coin is equally weighted and fair.

[john656656]

u might be the next Albert Einstan or the biggest retard i have seen so far on youtube.

[calvinhobbesliker2]

Because I noticed that a coin toss isn't a phenomenon that works by chance, but by the laws of physics?

[john656656]

do you also apply law of physics to love making? speed of thrust, body position, room temperture,angle of thrust, vagina resistance, your weight.....etc.

y do not you spend your time reading some get rich book? This suits you more.

[calvinhobbesliker2]

Reading a get rich book doesn't suit me more than trying to look at all possible causes for a physical phenomenon.

[john656656]

please explain y you are here on youtube. The fact that ' you are here on youtube' is a physical phenomenon, so pleas explain scientist.

[calvinhobbesliker2]

I am here because i typed my username and password in their corresponding boxes

[kinghaha1]

why cant u put adsense on your website

[colemgt]

I doubled up and lost nine straight times ($127.75) on $0.25 computer roulette that only had a single 0 in Las Vegas. What is the probability of that? Maybe God does not like me.  Anyone have a quarter.

[Psyzoid]

not getting any heads would suck.

[thewayoutisin]

HAHAHAAH Yes it would. I want to get Sal a really beautiful girl to give some heads... maybe some tails too lol. Sal, I'd be so cool if i ran into to you at a bar. i would love to get wasted it with you bro lol.

[Krissam2k]

well he's a bad better then.

but yea, if he keeps betting eventually he will break even.

I dont know if he covers this in this vid (im typing as im watching because i know the stuff he's going through atm :P)

but assuming that he bets randomly between 2 teams and loses 13 times in a row would be ½^13 = .01%

[Roshibear]

It's not true that he'll break even unless he was betting on teams randomly. Also the terms of particular sports bets aren't spread against the chance the team will actually win or lose, but rather spread to ensure that the bookie's payout is even, i.e. that the same number losers as winners. The bookie then makes his money from the commission he takes on each bet, known as the vig, and not on the actual odds that the team is going to win....

[Roshibear]

So betting at random should not produce break even results.

However, since his current performance is apparently much worse than random. He ironically has a greater potential of breaking even by increasing his stakes and then picking his teams at random then he appears to have by applying whatever strategy he has currently been using. However this is not a strategy I would necessary suggest either. It's simply a marginally better alternative than whatever he had been doing.

[thecrowlord]

I know someone who lost somewhere around50,000 dollars betting on baseball games! He lost 13 in a row w/ the idea that bringing his bet up to what he has lost he could break even.

[Roshibear]

Was this man's name, Pete Rose?