Probability (part 7)

[@khanacademy]

Don't worry about it. Some people use the Internet to vent their negativity indiscriminately Appreciate your comment..

[@jehotanyoung4546]

Just want to say thank you very much for doing this, your videos have been helping me a lot! Keep it UP :)

[@Fyrius]

A visual approach to Bayes' Theorem? I love it! :D This makes calculating conditional probabilities so much easier for us numerophobes. :)

[@BethLeonard]

@langengro -- To clarify even further, what he said was correct, what he wrote down was wrong. He did write: P(5/5 | N) * P(N) = P(5/5 | N) He should have written: P(5/5 | N) * P(N) = P(5/5 ∩ N)

[@Cooliorodriguez94]

At 4:35 "Probability I got 5/5 and the normal coin." The symbolism you used to represent that indicates different.

[@guambi1]

@InsanePorcupine - many people commonly find this concept confusing. Recall that probabilities have to do with a large number of trials. In this particular case, you as the coin tosser are a single trial. Every time you flip the coin, the coin is not aware of the previous coin flip, hence the fact that each flip of the coin is an independent event. Intuitively, it would seam ever more improbable that the next coin flip would also be heads...

[@DK2009]

Superb explanation. Upto now i just remembered the formula of baye's theorem and did these type of questions .But your explanation made me realise why this came.

[@dekal22x]

Teach them Bayes method for this as well. It is very powerful for these questions.

[@amardeepbhatia6232]

Wish we had teacher like these when we were in school. Anyways, in this age of internet, anyone can study from any part of the world.. The only thing needed is willingness to learn and grow! Thanks for such nice and simple explanations.

[@MatteNoob]

good video as usual, Sal. :) You are my favorite mathtutor on the internet!

[@bipros7]

Now i got the concept of bayes theorem and its applications as clear as daylight

[@willawanders]

he did: P(5/5|N)*P(N)=P(5/5|N), that means: P(N)=1, but it's .9

[@marieshwarankaliappan1559]

I have never saw such clearly explained video lectures in maths.. thanks a lot..

[@MrCheeseguy123]

WATCHING THIS 40 MIN BEFORE MY MIDTERM...FML

[@InsanePorcupine]

Never mind people I think I have figured it out on my own. Or at least cleared up some misconceptions I had about things. I now understand that my odds of say getting a tails in six flips is 98.4% however my odds of getting said tails goes down with each failure contrary to what you might think. 98.4, 96.8, 93.75, 87.5, 75 ,and then finally 50% for the last flip. Funny that before you flip the first time you have increased odds of getting tails but your odds dwindle with each failure.

[@cheney026]

I know that this is a little 2 years too late but if you have missed the question discussed here it could be quite confusing. Watch part 6 and see if its any help

[@wofong]

Watch Probability (Part6). There you can find that P(5H | Normal coin) * P(Normal) = 1/32 * 9/10, and P(5H | 2sided coin) * P(2S)=1*1/10. He's trying to explain that P(5H | Normal)*P(Normal) = P(5H AND Normal) using graph...

[@FilezillaDownload]

I love these Khan academy videos.

[@LucianoAlakija]

hi khan, just a point on 4.38 you draw GIVEN but it's AND

[@guambi1]

@InsancePorcupine - cont... However, consider the following. We can calculate that the probability of 6 heads in a row is approximately 1.6% (0.5^6). Note that our single trial assumes exacly 6 flips of the coin. How can we think about the real world interpretation of this probability? There are several ways to think about it. In one instance, we can interpret this as the probability that on any given trial/experiment of a set of 6 coin tosses, there is 1.6% chance that you will get all heads.

[@gforceram]

lost me there but im gonna watch it until I understand it.

[@JBoydJBoyd]

Thank you Khan Academy. I'm a bit confused though, on one point. To me, the probability that you got the two-Heads coin GIVEN the fact that you got five Heads means: after you get 5 Heads, what are the odds that you picked the HH coin. That would mean you have a 78% probability, since 32/320 divided by 41/320 = about 78%. We're talking about AFTER you get 5 H's, not before. So we're only talking about the part on the right that is circled, right? and the HH coin accounts for 78% of that. Can someone show me where I'm wrong here?

[@rodrigo_t9]

I think you're right, Khan probably forgot what his original question was.

[@elpresidio]

Let me see if I have this straight. I know it's a while since you watched this video, 5 months. but 9/10 is the probability of a normal coin, 1/32 is the probability that from a set of only normal coin you get 5 heads, and 1/320 is the probability that with 2 sided head biased coins which accounts for 1/10 of entire rectangle mixed in with the normal coins that you get heads from only normal coins, correct?

[@guambi1]

@InsancePorcupine - cont... Another way to think of it is that if you conducted 64 experiments (trials) of flipping a coin 6 times, you would expect at least one trial in which you got all heads. Yet another way to think of it is imagine gathering 63 of your friends and everyone including yourself had a coin to toss. If everyone simultaneously tossed their coin 6 times and recorded their results, we would expect at least one of them to have gotten heads on each coin toss.

[@InsanePorcupine]

one more thing if anybody reads this thats been messing with my head and the reason I started watching these vids is if you flip a coin 5 times and get heads every time your odds of getting a heads on flip 6 is still 1/2 yes but is it? I have trouble grasping that 6 heads in a row is 1/64 yet your chances of getting a heads is 1/2 when if you got one it had a 1/64 chance of happening. Your odds of getting a tails does not increase at all? shouldnt the odds of getting tails go up.

[@marieshwarankaliappan1559]

your lectures are really clear..

[@sshaikh8104]

Very nice explanation I wonder why people write bad comments!

[@Mikej1592]

Just one thing bothers me about this, all coins are two sided (not counting the edge) you mean to say a 2h or two headed coin.

[@KuroBot69]

A coin with 100% chance to give heads when flipped.

[@AKAciti]

These classes are very interesting

[@bookluvr613]

im taking the algebra regent on the 16th, and i didnt learn probibility yet, so im using these videos. but is all of this on the regent?

[@clarkindee]

Love your videos, Sal. You lost me a litle on this one but thats okay, I've watched all the others up to this one so probably just a litlte tired LOL!. Bless you for your work on this.

[@lilmizsudan]

I am confused to the bone.....I have now lost it....seriously I don't understand....at around 02:35 were you talking about And/Or Rule....if anyone understands please shine a light on me....I've got my Sats.....Year 9 Sats...yes I live in the UK...in about 2 to 3 weeks but I still have trouble with probability....so please people...

[@InsanePorcupine]

can someone explain this to me if your odds of getting 5 heads is 1/32 on a normal coin then how come your odds of getting 5 heads when you have a bag of ten coins with one false one go down for a normal coin. Its just confusing I understand you have a pick of 9/10 coins but it just seems counter intuitive that your odds would decrease to about 1/35 but I guess the extra probability in the 1/10 makes up the difference?

[@BestTheGuy]

So, what's the intersection part of a∩b? I've a feeling like the author wanted to say a∧b, does he?

[@Vinay123456143]

Perfect !

[@BlvdBroken]

why cant i get what im looking for! :C

[@shazaduh]

I think it's a typo. It should be P(5/5 and N) where "and" is intersection.

[@HotPepperLala]

4:38, it should be P(5/5 AND N)

[@ritesh024]

@langengro it means the same thing.

[@drakezen]

Botany bay? Botany Bay?!! But seriously, great videos! :)

[@langengro]

typo at 4:38 - should be AND, not GIVEN.

[@dekal22x]

Guess I should've watched the whole video first.. nice

[@marieshwarankaliappan1559]

if any one don't understand this, please watch previous series, I guarantee u will get cleared on concept..

[@juvrajgarha4085]

UR DADS A GOOF

[@sergiohater]

This particular segment has confused me more...will have to find another video to help me. Sorry to say but I wasted my time on this.

[@I_Am_Midnight-i]

Why? lol

[@askshbni]

very nice thnk u

[@doncharted]

it's KHAN from the epiglottis. Kh, kh, khan...KHHHAAAANNNNNN! XD

[@MBlu3]

this looked like the starcraft ui from the thumbnail :))

[@erikapk]

@penguinluther Haha, me too!

[@schtekar]

lovely

[@mubarakhabab8673]

wonderfull

[@Rook1515]

THANKS!!!

[@ericd6035]

lost at Probability of# 2s coin out of 5heads coins,

[@wiwiudiuhne]

good

[@valibaimoukhametov6795]

good info, filmed on a toaster

[@jpcgandre]

p(a|b) is not p(a) times p(b)!!! if they're independent!!! if they're then p(a|b)=p(a) dahhhh

[@lucas_vasconcelos]

cool

[@94Hughesy]

240p ftw

[@mluce319]

This is the worst video out of the series, it would help to organize your thoughts before you record so that you are not constantly scribbling things out, going on tangents or repeating what you're saying.

[@BARaaz04]

He is also a human, no big deal. I have been watching the probability series from beginning. If you watch previous videos it will be clear to you.

[@letian1299]

Horrible writing which by the first half of the video becomes unreadable so you cannot understand where is what. Waste of time.

[@RudeGirlSwagger98]

The guy lost me after the p=(a/b) shit