Probability (part 1)

[@Lettime1]

Guys you are not forced to watch the video.For that reason ,I you dont want to watch this ,go ahead and watch what you feel like watching.Do not discourage those who understand this type of teaching...Keep it up Proff ,you are my God of Math !!

[@khanacademy]

A "frequentist" wouldn't say that if they have a history of all heads, that the next toss would be heads. A frequentist would say that any toss has a 50% chance of being heads. The wikipedia entry on probability explains this further.

[@jmb120]

So it's basically just a calculated version of confidence and doubt?

[@mrpkmnfrk]

3:42 well damn that escalated quickly

[@Lilkevtalk]

Cry LMFSOO

[@Nixie_536]

😂🤙🏻👌🏻

[@willawanders]

he says, "the probability of picking heads on a die". LOL!!!

[@dylanlomanto5796]

Using this for a college Stats class because my professor is horrible. Thank you.

[@raytee1999]

i feel like i am hearing John Mayer talking! The resemblance is insane!

[@chloecomeau1357]

Omg!! So true!!!

[@anticorncob6]

@MajorNourhaghighi Suppose there is a 1/4268 chance of getting locker 2134 (2134*2 = 4268). If 2134 thieves strike, the chances at least one will hit it is: 1 - (4267/4268)^2134 = 39.4% That's not something to take chances about, so you should either have more lockers or make this one more secure.

[@ishmartishtiaq371]

Its been 13 years since video still its mesmerizing

[@johnstevens1155]

This guys voice is so fucking soothing.

[@bgstardust1]

ikr

[@psychodriveskip]

@anthonychemistry The individual events are independent. The first flip and the second flip have the same 50% chance to land on heads. However, when taken as a sequence of events, the calculations are correct. In Khan's words, the experiment hasn't ended until after the second flip. If it helps, you can count the number of (equally probable) events. In two flips, the set of events is { TT, TH, HT, HH }. From this, you can see that HH only appears once out of 4. That is, 25% of the time.

[@MajorKeyvanNourhaghighi]

Hi, please let me know, what is the probability of event that: Among 2629 lockers, in 50 rows "one particular locker -number 2134" be targeted by a thief? The other factors that may be considered is that locker 2134 is located in more safe area than others. Thank You

[@chrisdonovan5694]

I... I don't do videos on spelling...

[@panditbelkar9013]

Chris Donovan xddbdhch

[@mantlevee_k4818]

😂😂😂

[@alektad]

if Sal says you can get Heads with a Die you better believe it :D Sal is a genius, we all make mistakes, so lighten up

[@zittlezach]

xD so true so true..

[@rileyg1307]

Is he converting even numbers to heads?

[@rimtech2015]

With a random play your chances are 1 in 42^6 or 1 in 5,489,031,744 However, there are several ways to *select* lottery numbers that will increase your chances of winning. This is done using data from past drawings, and these systems are called "lottery wheels".

[@Jackies1979]

you could have mentioned the propensity theory of probability (my favourite): the prob of a die to show 6 is a physical propensity/property of the die just as is its mass, density etc. it solves almost all the problems of frequentism at least... what in frequentism would be the probability of the truth of the statements "there are tachyons" or "all ravens are black".... probability of events only once occurring? 1??

[@micpax1]

Man... your videos are PERFECT. I wish I had them when I was at school..

[@anticorncob6]

@novatodeguitarra No. The probability of getting heads on a coin 5 times in a row is 1/32. The chances of getting it 6 times is 1/64. The chances of getting heads the sixth time isn't 1/64. It's 1/2; when working out the chances of it happening the sixth time you also have to know that there is a 100% chance of it happening 5 times; it already did. For the sixth time you ignore the first five flips of the coin, and get the answer 1/2, which is the correct answer.

[@gameofdeath19991]

@sdrulz your question is related to conditional probability wich is coverd in other videos of khan.... the answer is: 1st= 0.95*0.01=0.0095 ( which is just the probability of choosing an innocent person out of the pool and then multiplying the prob of judging him wrongly (guilty)) P( Innocent but judged guilty)= 0.0095 P( guilty and judged guilty)= .05*.90=.0405 P( Guilty)= .05*.90 + 0.0095 =.0545 Now that we know that hes charged guilty, the prob that he is innocent = 0.0095/0.0545= .1743

[@askshbni]

i used to detest probability...i could just not figure out the answer to any question however much i worked hard.....it seemed so ambiguous...but now thanx to ur detailed & lucid explanation...i'm able to catch up...:)

[@alexgreenleefilms6927]

This is not a movie sir. Movies are developed for entertainment.

[@kisematooraseangean6986]

looked sooo much to find this comment

[@sadavar3746]

at 9:12 he says "Well lick at it this way" xD

[@darkhawk7746]

+Varun5 Lol YEAH ;))))))DDDDD

[@propickle3942]

that is funny

[@anticorncob6]

@Mawz11 The probability of heads seven times is (50%)^7 = 0.78125%, not 14%

[@OMARZAKIALIRAQEY]

cool

[@mr66697]

this tutorials is excellent all, all your probability tutorials always are

[@monikachenkus543]

Thanks Khan Academy you have helped me daughter soo much!

[@korathiren14]

@3s3guero916 Yes Sal graduated from MIT, BS in mathematics and his MBA from Harvard Business School.

[@jamesivan24]

Five items are randomly arranged. Is the probability that they'll be in any given order 1/(5!)?

[@SandeepAmilineni0]

Mathematics for calculating chance? i dont think it can be called chance. Instead we can rename as total output/total possibilities

[@etraderx11]

just a thought, when they talk about rain they could also refer to a larger area 50% of which WILL get rain and the other 50% WON'T, but they don't know which one WILL and which WON'T

[@TheUnknownFactor]

I just wanted to comment on this. You state that "if the probability of result [x] is 50% and you did this experiment 100 times, the result would be [x] 50 times"- this is incorrect. It's essentially like saying, if I flip a coin twice- one will be head and one will be tails- which simply won't hold true. What is true is that if you did this test an infinite number of times, half would be result [x]. That said, I love this stuff- keep it up.

[@hip2thabone_da_sticky1]

" I could get heads or tails, " says sal. I never knew sal was a true playa! ;-0)

[@ArjunDaveDY]

@cuzimaog8 Cheers guy, but as you continuing tossing the coin, to correctly predict 'x' many correct in a row the probability decreases, someone explained it to me. basically to get one is a 1 in 2 chance (1/2), but to get two in a row is 1/4, and this continues. See i wanted to know how to predict , getting 5 right in a row and the chances there are 1/32.

[@2CSST2]

I live in Montreal and it happens often that when the wheater man says there is 50% of rain/snow(winter) tomorrow, there is no rain/snow at all in all Montreal. in fact, close to 50% of the times. Maybe if you think about a very large regionbut then what's the point to say the example is wrong, he didn't specify it was for a very large region you're just making it up for, I don't know.. the pleasure of saying he's wrong... no point...don't do that unless it's a real mistake we can care about

[@bean2594]

The frequentist perspective also requires a hypothetically infinite number of trials.

[@Mawz11]

Quick question. What is the probability of an event with a 50% chance of happening, happening seven times in a row.

[@amusagete]

flav666, the butterfly effect was simply to illustrate the point that it's extremely hard to get two cased in nature that are exactly the same (b/c even one little difference in the environment can affect the case)--so he was actually ON topic the whole time. Maybe to some people, this obvious connection is not obvious?

[@anticorncob6]

@MegaMattcar probability = (1/2)*(1/6) = 1/12 doesn't matter whether you flip the coin first or roll the die, it will still be 1/12

[@OSKARSY11]

Hi. Perhaps you could help me. If there are 6 greyhounds in a race, and they all have an equal chance of winning or coming second place, and if I put money on four out of the six greyhounds, what are the odds that one of my four selections will be successful (that is, how likely is it that either one of my four selections will come first or second)??? Hope you can help me! Cheers!

[@Fangornmmc]

I deem probability to be: "The likelyhood of a certain event to occur"

[@andriaphilippou5230]

Can you please tell me the software that you use to do this ? ( i mean the black-board and stuff). Please let me know ^^ Nice and helpful video

[@raxxrulez021]

what is the probability of winning in a 6/42 Lottery? hope you can help. thanx

[@malikjunaid1]

at 1:05 I think Your statement is wrong. I think it should be 100% means he is sure that it will rain tomorrow and 0% means He is sure it will not rain tomorrow.

[@floridarico2012]

can you help with GED math? like more word problems and such?

[@Mawz11]

@anticorncob6 Yeah, it is. I use that probability in gambling quite often.

[@blacksilkblacksilk]

I know perfectly well what you mean, dude. The man`s a life saver. Would have saved me hunderds of hours of frustration. Just GREAT. have a nice day silk ;-))

[@ArjunDaveDY]

Could anyone help with this problem? If I flip a coin 'x' times, and alternate between predicting Heads and Tails, is there a way to get the probability that I will guess right/wrong every time. and is it possibly to know how many times something has to be flipped on average to get the prediction. Like if we did an experiment on average how many times would someone have to flip a coin to predict correctly? If anyone know's how to figure this out would be awesome, if not thanks for your time.

[@sdrulz]

A truth serum has the property that 90% of the guilty suspects are properly judged while of course 10% guilty suspects are improperly. On the other hand, innocent suspects are misjudged 1% of the time. A suspect was elected from a group of suspects of which only 5% committed a crime and the serum indicates he is guilty. What is the propbability that is he is innocent? Can someone help please

[@mgunar]

I second that. How about a video series on Real Analysis or Abstract Algebra? The amount of resources available for "elementary" math is overwhelming. By elementary I mean the math that say, a typical engineer would take: Calculus (I, II,II), ODE, and Linear Algebra. However, beyond this, starting with PDE, and continuing to Analysis and beyond, resources become scarce. These are not "popular" subjects; however, there are those of us who would love to see video lectures of these topics.

[@balsyitlog]

"i don't do videos on spelling" LOL

[@renduke]

help.....if red happend 120 times and blue happens 67 times what is the probability of red ? is it 120 divided by 120 + 67 ? or would that be the probability of blue ? or is it neither ? how does this work ?

[@mdsleboda]

Why didn't you ever finish up with the rain chance you started with??? You never finished to show how to figure this. you went on a ramble about other things.

[@MetalSio]

No matter what class I take, the place I end up at is Khan Academy!

[@MrZola1234]

Great explanation, can't wait to listen to some other videos by you. I have a probability question. Lets say I am a trader, and I want to figure out the validity of my winning percentage. If I know some variables related to my trading system, such as winning percentage, amount won and lost per trade, maybe variance, is there an equation that can tell me how many trades I need to to make to ensure my winning percentage is vvalid/relaible to a certain degree of error? Zola

[@BenHayward110194]

The closed captions should read "50%" at 09:15, not "5%"

[@markerat]

time index 7:58 i am flipping a fair dice whats the probability of getting a heads. I tried flipping a fair dice 100 times and i never got heads or tails. Please explain what i am doing wrong ? Good video series, i love your stuff.

[@floopy312]

Dude im speak spanish and im learning english.. if you could speak more slowly sometimes i could understand you much better and easier... Thanks anyway for all your video posts.. they are excellent... Remember that your videos can reach any spot in the world and reach most of the 6billion people that live in earth and most of the time this people can just understand plain english.. like me :) PD: i really love ur explanations about the financial crysis.. i learned a lot

[@chadmcdonald22]

how many parts in total are there for probability?

[@sushilavale3630]

0% is sure that it will not rain

[@taekwondoemoboy]

I guess it should be 1/3 , I got it by dividing the number of games at which the team scored more than 2 over the total number of games.

[@vi0lat0r84]

@treefangers he is talking about a coin not a dice .. he said it wrong g-money

[@Romeowasbleeding1]

You're a good man. I would love to know how you profit from this

[@habibakhatun9031]

All the haters of this show are crazy and this is a dhamaka,awesome sow thanks,mr.khan......

[@ralphnathanielalpanghe7917]

Probability of getting friendzoned???

[@cheshirenevande4701]

+Ralph Nathaniel Alpanghe Based on length of relationship....anywhere from 80-98%...

[@ivyy11]

Depends. For example it's 100% for me.

[@natashanajam3499]

+Enes Tashkandi with that as your profile picture , I'd have to agree

[@heliumfilledweeb3215]

100%?

[@myreid]

Depends on the person, for example if u are in a school where cheerleaders always or most of the time end up with a jocks and u are a jock that likes a cheerleader, or vise versa somewhere between 30% to 50% cause she might like another guys. IM TRYInG TO BE PROFFESIONAL DONT JUDGE

[@cheney026]

I kind of got mixed up with the play list order and then Probability part 1...:(...anyway great videos Mr.Sal.Keep it up.Your helping me out a lot.

[@dlux4693]

What if it os neither something out of something?

[@superelaaaine]

Thank you so much! I understand it now, compared to my double-class algebra at school.

[@joaquinsaldarriaga6281]

Hi Khan, in the prob. problems, when I put the answer, IT CHANGES THE QUESTION!!! FIX THAT PLAESE

[@vtkxrrxpted2683]

thanks alot it helped me

[@TheVibhavbisht92]

A lottery company sells only 12 ticket out of which 6 tickets are prize tickets. A person buys a total of 5 tickets.what is the probability that he wins at least 1 prize? Please reply guys with explaination.

[@roarmaster2]

can i request you do a video or a tutorial on bearings please and fast

[@robertwc82]

what if i rolled the dice for infinity, then the chance of me rolling a 6 is 100% but it becomes a matter of how regularly it occurs. the chance of life emerging in the universe is 100% because time, matter and energy are infinite and as we know it is a possible event though improbable

[@jonjonjon1370]

@Mawz11 I think it's 14%?

[@Violet_roses45]

i still dont get it , so much for a good mark on my final

[@عمراحمد-ت7ق]

A coin is tossed twice calculate the Probabilities: 1-the appearance of at least one head 2-the appearance of at most one head answers: 1- 3/4 2- 3/4 how it was in 3/4?

[@douglaspool4838]

If you break down the scenarios into all possible outcomes it becomes clearer. The outcomes for tossing a coin twice are: HH HT TH TT Now for outcome 1: The appearance of at least one head (one or more head). Of all possible outcomes, HH HT and TH all have at least one head. so 3/4 For outcome 2: The appearance of at most one head (one or fewer head). Of all possible outcomes HT TH and TT all have at most 1 head. so 3/4 again.

[@TheJebacina]

Salmon please do some mathematical multivariate stats

[@jaclac911]

what's the probability of getting 3 10% chances in a row?

[@FrozenFlashDrive]

I flip dice sometimes too

[@dianaxo9638]

VERY helpful thanks! My statistics professor is not the best instructor

[@JesseMaurais]

There's at least one more way to define probability; as a feature of a model conforming to the Kolmogorov axioms. Also there's a old joke about Bayesians and frequentists. In a coin toss experiment, the Bayesian will sooner expect an unfair coin.

[@nonchalant-turtle]

Heh... third in my honors math class, going to AP next year, and I don't get probability. Or at least, it didn't interest me as much... *watches and learns*. I succesfully learned and applied the binomial theorem using khanacdemy, so, awesome :D.

[@sujatasantosh2989]

Sir we just learnt about yon in my moral science book 😌

[@0001-exe]

'Butterfly effect.' Reminds me of until dawn

[@blubberydew]

P`(A) - probability to win no prize at all. P(A) = 1 - P`(A) - probability to win at least 1 prize. n = C(12,5) = 12!/5!*(12-5)!=792 - number of all possible 5-element subsets. m = C(6,5) = 6!/5!(6-5)!=6 - number of all no-win 5-element subsets. P`(A) = m/n = 6/792=1/132 - probability to win nothing. P(A) =1-1/132=131/132 - probability to win at least one prize.

[@Dalwanaage]

@4u2nvdfx Man u don't get it. He is talking about not a dice it self but has got 6 numbers from 1,2,3,4,5 and 6. And these 6 numbers can be divided into two groups namely even and odd numbers 1, 3,5 and 2,4,6. Ok . Look carefully at it now . You have 6 numbers where three of them are even while the other three are odd numbers. So what is the chance of getting and odd or even number after rolling the dice. 50%, so Salman is right. THanks khanacademy.

[@Ceonsamea]

@sdrulz 95%. Regardless of what the serum indicated, you said yourself that only 5% are guilty, meaning the other 95% are innocent. It was a trick question right? :D

[@andusgarza497]

When I'm flipping a die.. lol

[@Eazz34]

DPx111 Yes he mistakenly said dice when he meant to say coin. Again, why I suggest he slow down and disregard the time limit. But overall does a nice job!! :)

[@lumel666]

wow bash the guy who is taking time out of his life to try and pass his knowledge on to you without any obligations.. you sure are smart

[@Jay88891]

proabability of rolling a dice and getting heads? LOL 7:57

[@LightningBoyNation]

lol

[@arthurwashington5881]

Lol

[@keshavbhardwajpkl3742]

popat

[@peterpie2258]

probability of flipping a dice? PROBABILITY OF FLIPPINNG, A DICE????????????????????????????????????????????????????????????????????????????????????????????? 7:56

[@michelegalli174]

He has 3 degrees from MIT do you?

[@fawaz70]

michele galli OO tell em

[@cheshirenevande4701]

+Peter Lafranchise You should try it. You get more interesting results that way.

[@jasonlouis9140]

Peter Lafranchise and roll a moron like you ..

[@adambamber4958]

Lol good to go back through the old vids :p

[@multiv3rsegamer754]

My mum made me watch this and she made me do khan academy, Ya boi got 100% on Kindergarten /:)

[@multiv3rsegamer754]

Btw I am year 8 (7th grade)

[@mannymanolios4217]

10 years since this video was uploaded

[@nileday120]

Thanks Khan!

[@panda00303]

Thanks, probability got confusing after a while in school. I think the teacher got lazy, it was near the end of the year.

[@puggygirl6]

How about Theoretical Probability

[@peacedudepeace]

99% 10%x10%=1% of being late (sorry for the writing i'm french) you have to claculate the probablilety of being unable to do it like if you have 1/3 of having good answer and you do it again and again you have to do 2/3x2/3x2/3... so you will never have a 100% so alwais have it Thx Have a nice eavning or whaterver it is when you read this

[@MrDaBBaS]

I don't understand this very much, yet I never get them wrong ;)

[@ubentu]

@rami1ify He wasn't making fun of the middle east. He was making fun of public perception.. You have to catch his humor in all of this.. I mean.. the weather.. THE POSITION OF THE MOON?