Calculating conditional probability | Probability and Statistics

Calculating conditional probability | Probability and Statistics | Khan Academy

Рет қаралды 968,485

10 жыл бұрын

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Пікірлер: 148

@rahulsbhatt 5 жыл бұрын

I m Rahul, and I approve this 💫

@mariselalopez55 5 жыл бұрын

Rahul Bhatt 😂

@wandererrrrrr 3 жыл бұрын

🤣

@mitchellshoniwa7695 3 жыл бұрын

😂😂😂😂

@kevinfarrell9304 8 жыл бұрын

rahul got hella cholesterol

@santhithiyagarajan1493 6 жыл бұрын

Kevin Farrell i

@RahulRana1 6 жыл бұрын

chill

@ruru7458 4 жыл бұрын

Rahul Rana AHAHHAHA

@Rahul-ef2ou 2 жыл бұрын

Ayo blud, man’s hella fit. DONT CHAT TO MAN LIKE THAT 😂

@akirarae.m 2 жыл бұрын

💀

@ladyammox8314 7 жыл бұрын

Thank you! It's always disappointing when I finally learn the material that I struggle to understand just to find out that it was actually quite simple.

@aaaquascaping9774 2 ай бұрын

IKR

@socialistcna6061 3 жыл бұрын

This requires you to already know how to calculate conditional probability. In the third line, in yellow, you keep re-using the number 0.35, without which you could not have solved the problem. But getting the 0.35 required you to already know how to solve the problem P(A|B) which is already caclulating conditional probability. It doesn't do any good to tell someone that they need to know how to calculate conditional probability before they learn how to calculate conditional probability.

@mikecherri 4 жыл бұрын

Gosh I’m still confused!! I gotta rewatch this at a later time maybe it would make a difference

@putiest4821 4 жыл бұрын

Me too haha!

@nhuvlog1127 2 жыл бұрын

I’m about to have a test on these and im so scared 😭

@miguelmontes5242 5 жыл бұрын

Dont get the logic of the formula P(A and B) = P(A|B) * P(B). But this channel is fantastic!

@MrArielnyalila 7 жыл бұрын

I khan not think of anyone who would explain this like you

@andrewsulaiman5639 4 жыл бұрын

I khan da wanna throw up

@aivmie999 4 жыл бұрын

@Nayarrrrrr Жыл бұрын

Finally able to understand this topic...... For 5 months been struggling and u just washed it away in a matter of 6 minutes. Thank u

@Barbs102859 10 жыл бұрын

Thanks man this is exactly what I need help with. YOU are a life saver my friend! God bless you. You beautiful being!

@theknightgirls 6 жыл бұрын

totally understand dependent and independent probability now, thanks so much! i have a unit test tomorrow.

@sandygan4054 4 жыл бұрын

Thank you very much, this is easy to understand & very helpful!

@optionstrader4624 4 жыл бұрын

The way I was taught P(A and B) was like saying probability of (A and then B) ... From this it makes intuitive sense that it follows P(A) *P(B|A) because A happened first ... Not sure how you can switch it to say P(B) *P(A|B) without switching it to say P(B and A) which we know P(A and B) is not equal to P(B and A)

@vizuboygaming 3 жыл бұрын

The biggest thing is writing out what you know. What is P(A)? P(B)? P(A|B) or P(B|A)? They have to give you some information. Once you write out what you know, you can find out what you don't know. Also, making a table helps as well if you are more of a visual person.

@anannyasaxena7896 6 жыл бұрын

Rahul is an indian, he eats parantha for breakfast and chawal for lunch.

@gary7536 6 жыл бұрын

Anannya Saxena that is my exact diet

@rchtchauhan 3 жыл бұрын

Indian*

@rahulsbhatt 3 жыл бұрын

Approved 👍

@bobproctor-ev4bc 3 жыл бұрын

lol, right !!

@aravsingh2588 8 жыл бұрын

I was trying to find out how to find P(A and B) and I was searching all of this up on google and kept going in circles without an answer spending 10 minutes struggling. I come here and get the answer in the first 3.5 minutes.

@CreeperG0d 2 жыл бұрын

Man thnx so much, I was struggling with this. But now I found the solution, useful explanation for any similar problem.

@MrJ3 10 жыл бұрын

VERY informative and simple video.

@johnnikkie1429 6 жыл бұрын

Take a shot everytime he says probability ;)

@Oogabooga46587 3 жыл бұрын

Alcohol poisoning

@straightoutofstrat8722 7 жыл бұрын

Omgness l just about understand this let's see if in two hours time I have managed to retained this information. If l do well l have managed to surprise myself.

@felipegarcia2269 6 жыл бұрын

I never comment but I hope this finds you ... you are the greatest teacher ever

@BossGIsaac 7 жыл бұрын

thanks, helped a lot

@GigaLordShinyMudkip1 7 жыл бұрын

Thank you very much.

@JariMustafa 10 жыл бұрын

Thanks. This helped a lot :)

@ViolinistJeff 4 жыл бұрын

I think you should mention that we´re looking at the events in the day as non-linear space time, just as Einstein saw it, because if you look at it as a regular time line you will get confused. I mean, how does eating pizza for lunch affect the probability of something that ALREADY OCCURRED IN THE PAST, a decision that was already made (i.e. what Rahul ate for his previous breakfast).

@kedirhassen601 6 жыл бұрын

Thanks so much I understand it

@asmaaalhibshi2670 7 жыл бұрын

You sir are awesome 🙏🏻🙏🏻

@vwlz8637 6 жыл бұрын

Just ate a pizza for lunch! Travelling back in time to eat bagel for breakfast!

@viraj_singh 6 жыл бұрын

Actually you've used Bayes theorem indirectly. This could be a good way to prove Bayes theorem.

@damienpride9860 Жыл бұрын

Makes no sense

@user-dh3yo9eu1j Ай бұрын

Me also.

@erriedigtal 8 ай бұрын

thank you, you explained it better than my professor :D!

@zoeschipper4311 7 жыл бұрын

This is so damn good!!! Thank very much!

@dannyclub09 4 жыл бұрын

I understand it up to 3:40. Can anyone explain it? He says that P(B/A) x P(A) is the equivalent of the aforementioned equation. But isn't P(B/A) what he's TRYING to find? So how can he start including it in the equation? And then he doesn't explain why he divides it by 0.6?

@Naddi_ 2 жыл бұрын

it is similiar to when x is in a maths equation. you want find that certain x and thats when you start to balance everything out.

@dannyclub09 2 жыл бұрын

@@Naddi_ Thankfully I'll never have to understand this again

@Naddi_ 2 жыл бұрын

@@dannyclub09 lucky, i still have exams this year and i cant wait to burn my maths notes

@homista 10 жыл бұрын

The ratio of P(A) to P(A\B) is 0.857, which is also the ratio that P(B) is to P(B\A). Is this true for all cases of dependent probability?

@DeViantwo 9 жыл бұрын

what is the program used here?

@redwings02 5 жыл бұрын

I don't understand the conditional probability P (A | B) when you can't eat breakfast before lunch. Doesn't the dependent variable have to come AFTER the independent variable?

@nt6987 7 жыл бұрын

very useful

@corey333p 4 жыл бұрын

Neat. Cool. Thanks.

@slowjocrow6451 3 ай бұрын

Who is the teacher. I want him to explain all my math to me. This is so well explained, thank you

@masumaakhter4946 5 ай бұрын

Alhumdulillah I've found this ❤

@noeggarcia19 7 жыл бұрын

All Hail Kahn

@jackfukin3089 10 ай бұрын

I think the biggest problem with probability is English Because this guy was saying find the intercepts given the conditional probability of one side (pause finding the conditional probability is intercept over the sample space of the condition) so to find the interceptor multiply the given the conditional probability and the sample space

@rafaeldelavega8193 6 жыл бұрын

this is definitely helpful for this midterm i have in one hour

@namiratajrin613 3 жыл бұрын

How'd it go?

@StimZlol 3 жыл бұрын

@@namiratajrin613 good thanks for asking

@StimZlol 3 жыл бұрын

@@namiratajrin613 I finally became a doctor

@beccaboo1820 6 жыл бұрын

#blessKahn I thought I was gonna fail my stats test , lol I prob will but at least I'll get a higher score than I would've if I didn't study 😂

@angelinebantillo3128 4 жыл бұрын

Did you fail?

@rhineyt5202 3 жыл бұрын

we can also solve this using bayes theorem?

@alexisarianna940 2 жыл бұрын

This is so complicatedddd like it just isn’t clicking in my head

@stevefriedlander7053 5 жыл бұрын

Where does the .05, .06 & .07 come from to begin with?

@InvaderG 5 жыл бұрын

Steve Friedlander the problem above mate. it gives you those numbers.

@hlpenguin8278 5 жыл бұрын

Read my man

@jacksonjoestar5035 6 жыл бұрын

Why does the audio of every video but Khan Academy videos play!? KHAAAAAAAAAAAAAAAAAAAN!!!!!

@stephenprice3357 6 жыл бұрын

this video confused me even more thanks

@philtrem 10 жыл бұрын

This is not how I've done it. I actually solved it mentally using the following logic: 1. The probability that B follows A (given that B occured) is 0.7. 2. B happens with a probability of 0.5. 3. The total probability of A occuring is 0.6, out of that, we know that (0.5 * 0.7) is the portion where A precedes B (or, B follows A) since B happens with a probability of 0.5 and once B happens, A has a probability of 0.7 of having occured. Essentially, this maps out as: p(B|A) = p(B) * p(A|B) ______________ p(A) I just hope it's correct. I must admit I struggle a bit with probability. I always try to solve it without formulas, using a problem-solving approach instead (manipulating the problem in my head and going around it)

@Ochxchii 6 ай бұрын

The fact that my teacher did horrible with explaining this, left me completely confused, just for me to find this video and realize it is quite rather simple.

@anoirtrabelsi8645 10 жыл бұрын

AMC ; AIME ; IMO ... Pleaase !!

@ishaanashwin2439 2 жыл бұрын

The way I did it was P(A|B)= P(A and B)/P(B) That gave P(A and B)= 0.35 So P(B|A)= P(A and B)/P(A) O.35/0.6 = 0.58333

@SkateWake1994 6 жыл бұрын

why does he multiply P(A|B) x P(B) and not add them instead?

@accumulator4825 Жыл бұрын

How can we make a conclusion about what Rehul wants for lunch, given that he has decided to have a Bagel for breakfast? Couldn't he have some weird preference for lunch for the specific scenario where he has already had a bagel for lunch?

@liwaiyip1769 4 жыл бұрын

For those who are confused why P(A and B) = P(A | B) * P(B) check out this probability rule. The rule states: P(A|B) = P(A and B) / P(B) So we put P(B) to the left side we get: P(A|B) * P(B) = P(A and B)

@mercury.833 2 жыл бұрын

Thanksss💜

@legend7890 3 жыл бұрын

P(A and B) = P(B and A). But, P(A | B) does NOT equal P(B | A). P( A | B) = P( A and B)/P(B) --(i) and P(B | A) = P(B and A)/P(A)-- (ii). We are given P(A | B) and to find P( B | A) we need P( B and A). We know that P(B and A) = P(A and B). We find P(A and B) by rearranging the equation i, and use the result as P( B and A).

@kunjanambitions 7 жыл бұрын

use this 2 formula p(A/B)=p(A and B)/p(b) and p(A and B)=p(A)*p(B/A)

@lifewithdylan 6 жыл бұрын

exam in 2 weeks!

@Joyce-iy9cg 4 жыл бұрын

dylan what up

@Rahul-ef2ou 2 жыл бұрын

Came to study probability, left wondering if i am obese 😞

@s1ight 3 жыл бұрын

why does rahul eat lunch before breakfast?

@juanespinoza-yx6jq 2 жыл бұрын

What’s the probability that (B) will happen if (A) doesn’t happen

@juanespinoza-yx6jq 2 жыл бұрын

To many missing information like how’d they come to .6 is he able to eat pizza for breakfast or is it that he can only eat a bagel for breakfast and only pizza for lunch and does he have to eat lunch and breakfast or can he choose to skip them if he can choose it’s just 2 out comes he eats or he doesn’t and also only 2 options of food pizza or bagel

@darksavior1187 6 жыл бұрын

The probability that Rahul will eat Bagel Bites for every meal is 100%

@hmunoz314 3 жыл бұрын

P(A & B)=0.3..... not 0.35? so it should be 0.5?

@junnom3029 6 жыл бұрын

Why does P(A|B)*P(B)? This is not explained.

@jasg9060 6 жыл бұрын

same thoughts. the irony when he said that P(A|B) is dependent to P(A).

@helloiamthechosenone 6 жыл бұрын

half of all lunches that R eats is pizza haha

@ViolinistJeff 4 жыл бұрын

So the problem said "On a randomly selected day, the probability that Rahul will eat a bagel for breakfast is 0.6, and the probability that he will eat pizza for lunch is 0.5. The conditional probability that he eats a bagel for breakfast, given that he eats pizza for lunch, is equal to 0.7." This is like saying that if Rahul eats a pizza for lunch, the probability of him eating (or having eaten) a bagel for breakfast increases from 0.6 to 0.7. Am I correct?

@rahul-xq4eu 9 ай бұрын

i'm rahul and i can confirm that i love bagels and pizzas 👍

@coldbrewed8308 Жыл бұрын

I have a question. What's is the probability that rahul eats pizza for dinner if he had it for lunch? considering same probabilities.

@baydenhiscocks2046 7 жыл бұрын

Anyone know what it means when A' has that symbol above it?

@leticiat1601 7 жыл бұрын

Bayden Hiscocks it means anything that is not A

@afsheenkhan6102 7 жыл бұрын

Bayden Hiscocks I think it means the image of A after a transformation You are talking about transformations right? It talks about the image of point A or whatever

@jakubaipldauer2786 6 жыл бұрын

Can someone explain me what does "given" in math mean? A was not able to find out how to translate it to my language.

@enochjohnson9149 6 жыл бұрын

It means what you already know. For example let's say " how many boys are in a classroom of 30 students, Given that 14 students are girls?" So we use what is given to help us find our answer because we already know it's value. So 30-14 = 16 By using what is given we came to the conclusion that there are 16 boys in the class.

@jakubaipldauer2786 6 жыл бұрын

Enoch Johnson Thanks.

@claytonwoodcock6942 6 жыл бұрын

How can this example make logical sense? One test subject (Rahul) was observed X number of days to give the probability of A and B happening (distinct values given for each event!). Now A and B are observed to happen on the same day. So how can you have a distinct number such as the value for A occurring and then a distinct number of B occurring GIVEN that they are both dependent on each other happening. I would argue that you could not have this example, A (as given to us here) can be dependent on B but B cannot be dependent on A this would create (in my mind ) a circular argument. How could you observe independent values for A and B if they are both occurring in the same system. If I am right then this is example was created by a none scientist. The only way ( that I can see) someone generating this question is if they have never performed an experiment. Otherwise, you would see the flaw in observing 1 test subject and coming up with Values (A or B) which are "constants" yet dependent on each other. This is an excellent example of how you can use math to get a number that means nothing.

@onepunchmanseason2epictv216 6 жыл бұрын

rahul is eating like its his last day on earth lol or he has a probability test tmr

@luciaremisova6248 3 жыл бұрын

I don't get how P (A and B) is equal to P (A I B)* P(B). If we were counting just P (A and B) we would use just a multiplication formula --> P (A) * P (B) = 0.6*0.5 = 0.30 not 0.35. Can someone explain this please?

@user-tt8gd9bw1i 6 ай бұрын

Hi! Did you find the answer to your question ?

@laughicious 7 жыл бұрын

next time please give us the formula first then work through the example instead of expecting us to work through it without the formula - thanks

@gunnercat8045 5 жыл бұрын

where the heck did he get 0.35?

@sherrythomas8359 5 жыл бұрын

im still confused

@papabear6431 3 жыл бұрын

They really just used B for Pizza instead of B for the Bagel

@liibbykniight 7 жыл бұрын

This doesn't make sense

@google-is-a-stupid-piece-o2543 6 жыл бұрын

It does, though.

@traxgod 5 жыл бұрын

3:32 it says "I hope this makes sense" what if it doesn't? I don't get it either.

@icosmini 5 жыл бұрын

It does, dough.

@tyshonwhite4743 5 жыл бұрын

Same

@thugjuice69 5 жыл бұрын

Tyshon White It does, though.

@roberts9590 8 жыл бұрын

how do you get 0.7?

@ThePunisher0313 8 жыл бұрын

+Robert Surrett it is in the question

@laurellion3567 5 жыл бұрын

This isn't really relevant, but why would they make Bagel for Breakfast A instead of B?

@cabfare4601 5 жыл бұрын

I was thinking the same, but yeah no big deal.

@PankajSingh-dc2qp 7 жыл бұрын

why u make it so complec. just use Bayes theorem.

@elon.2193 6 жыл бұрын

he just gave the intuition for it. People like you don't understand how and why something works and are almost like machines.

@RickyVWorld 7 жыл бұрын

What is the probibility that in an exam the guy in the question will have an Arabic name?

@prateekgurjar1651 7 жыл бұрын

Ricky Wheeler rabu! is Indian name

@prateekgurjar1651 7 жыл бұрын

Ricky Wheeler rahul *

@mabulemodiba9562 6 жыл бұрын

There are more things but I won't mention them cause I don't want to be 'That guy', I probably already am but...

@mehwishshah4979 5 жыл бұрын

Just ok🤨

@abrabr247 6 жыл бұрын

dont say a and b say the example meaning

@xagamers8109 5 жыл бұрын

0.5 divide by 0.6 x 0.7 lol

@TheBrownSugaBabe 4 жыл бұрын

divided again by 100 will give you 0.583333333 THANKS THAT WAS SO MUCH EASIER - my one question is this, how did he get 0.7 from 0.5 & 0.6?

@SR-kz9un 4 жыл бұрын

What? ! I'm so lost

@itsfabiolous 3 жыл бұрын

You calculate bayes and not conditional probability my friend

@cardguys 4 жыл бұрын

Ra-HOOOL

@TaiDye21 Жыл бұрын

This is still soo hard to understand 😭

@ViolinistJeff 4 жыл бұрын

The problem stated that the conditional probability of eating a bagel for breakfast is dependent on the probability of eating a pizza for lunch. The problem NEVER stated the possibility of the reverse: that the probability of eating a pizza for lunch could ever depend on the probability of eating a bagel for breakfast. So I don´t follow the logic.

@BaByEfrain 8 жыл бұрын

Katherine typically gets two types of alcoholic beverages at the bar. She will either order a midori sour 40% of the time or order an AMF. After her first drink, Katherine can either decide to order a water or another alcoholic beverage. If she orders a midori sour, she decides to get a glass of water 20% of the time and if she orders an AMF, she tends to order a glass of water 55% of the time. If we know that she ordered a water as her second drink, what is the probability that he first drink was an AMF?

@torlumnitor8230 8 жыл бұрын

60% with the given Info

@trevtv1004 5 жыл бұрын

I don't understand how come you guys can't just have easier questions or not repeat the same process for each problem coin, deck of cards none of these helping me

@jeremiahmathew3703 3 жыл бұрын

Don’t make sense

@adamlk100 6 жыл бұрын

QUIT REPEATING YOURSELF. WASTES SO MUCH TIME

@denden4455 3 жыл бұрын

Бред

@mabulemodiba9562 6 жыл бұрын

Mr Khan, can you please not waste so much time on things you don't need to do, like using different colours and 'mistakenly' using the wrong colour so you can waste time by erasing it and using the correct one. i'm writing an exam tomorrow and i don't have much time, all i'm saying is that the video would've been much shorter and your students could use the time to watch more of your videos, giving you more views. With all due respect. Please don't block me.