Expected Value: E(X)

[ls600h1]

What if there are an infinite number of possible outcomes?

Like for a continuous function.

The individual probability is ~0 for any one exact number.

How would I get an expected value

[petershayo]

you should get paid for this, seriously

[discy12345]

@petershayo donate! khanacademy . org/contribute

[00000gerat]

the video is admitted alright, though it doesn't really help with applying this to more forms in probability theory if you already understand this basic concept. real problem? if he says "arithmetic (n.) mean" one more time I will have to randomly distribute tacks all over his tongue.

[jaimitoteran]

Great video, thanks for uploading!

Two questions though...

The first value, when you multiply the probability by 0 (no heads), even if you multiply it by 0=0, you still have to put that probability (0.09278) in the SUM.

Second, why do we get the Expected value of 3, while when you calculate the arythmetic mean is 3.5? Should they both be the same? I really appreciate your response, thanks a lot!

[brian5446]

PLEEESSE make videos for quantum mechanics. This is so close, carries the base ideas, but using them with electrons looses me.

[chikentori]

#NUM! #NUM! #NUM! #NUM! #NUM! #NUM! #NUM! #NUM! #NUM! #NUM!

lol, I need to learn how to use MSexcel now!

[mumu8881]

so smart!

[dany2tah2]

YOU ARE THE BEST. thank you. thank you. thank you.

[ivankeri]

Hey! GIANT DOUBT.... How come the Expected Value won't be really the "most probable/expected value(s)" in some cases??????

(As said in 14:00 ) How could you interpret as an "Expected value" a non-probable value when it results form having very probable values around it?

[thesixthsense1]

Thank you very much sal .. Superb video as always..

[paulceltics]

thanks dog

[voidstuff]

THANKS! great explanations Khan! I love your teaching style

[cmason3344]

4:19 - number of heads after 6 tosses. lol

[jsstevely]

Hey I was wondering how to find the frequency of outcome when you don't have the use of technology. So without excel/graphing calculator how would you find the frequency?

[Anthony42ly]

Well, it 's AWESOME, or it's nothing.

[TheJrDream]

Khan you prove that south asians are indeed good at math. Way to go!

[jsteh22]

ur awesome! 

[thelastbattle19]

WOW!!!!!!!

[Huntsong64]

Oops hit a button. @babyteal2, I'm originally from America where I was in an advanced math program, and I moved to russia where the equivalent was three years ahead ... In 10th grade math now.

[Huntsong64]

@babyteal2

[RouksAdtas]

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[dalcde]

The expected value is actually weird the expected value when throwing a dice is 3.5, though you won't expect a 3.5 when you throw a dice!

[mattipihlainen]

@dalcde i wouldn't expect a 3.5 either!!!!!

[hyperthreaded]

These lessons are pure gold, and they really show what a multiplicator the internet can be by enabling smart people like you to kick off real revolutions just by uploading their thoughts and ideas and lessons or whatever else is on their mind to the net for all the world to see :-P Sorry, I wish I could express this more eloquently and less long-windedly, but I just want to say THANKS for these videos. And to think that they have been here for close to 2 years and I only discovered them today8-D

[EMRAlvarez]

that's a great video, however the population mean is 3.6 and the expected value is 3. So it cant be the same? Any reason as to why this is so? I cant think of a reason.

[joeybenn]

@EMRAlvarez. I believe they were two different examples. The first example being 3,3,3,4,5 and the second being the coin flips.

[TheAble2see]

@EMRAlvarez

you've made a mistake

expected value is the mean calculated with a probability and they both equal in this example 3.6

(3+3+3+4+5) / 5= 3.6

and

3/5*3+ 1/5*4+1/5*5= 9/5+4/5+5/5=18/5=3.6

best of luck to you !

[udaranga]

thank you sooooooooooooooooooooooooooooo­oooooooooooo much................. for 10months i was struggling with this population, sample and expected value . And every thing got solved within 14.52 minutes......... thank you very much....

I wish I watched this 10 months ago;............

[AnneAnne9102]

Thank You~!! ><

[Huntsong64]

Thanks! I'm in 6th grade and our probability book is teaching us basic binomial outcomes, but it doesn't really tell us how to do it (I was absent). I stumbled upon this video and realized the problem I was having was with expected value, not binomial probability. :-)

[babyteal2]

@Huntsong64 this is impressive. I had to drop stats at uni as I found it very difficult although I'm going to have another crack at it at a later date. Rather disheartening to find out a 6th grader can do it better than an adult graduate though :/ Hoping this video will help! Do you mind if I ask what country you are from?

[rakabali78]

I thank you thank you thank you a heap for all your videos (right now downloading stats, calculus, linear algebra, and geometry :) ). My current job requires me to pick up those things I learned back in uni (which I have forgotten almost entirely). Thanks KhanAcademy!!!!!!

[subticnewjour]

Kudos to Khan Academy !

I would request Khan Academy to keep posting more and more videos.

[bellarn0705]

Thank you for these excellent instructional videos. I am trying to teach myself Statistics, and I am hoping with your video series I can pass the DANTES statistics test.

[petitm1]

You Rule! Any plans of doing some modern physics? or even Maxwell's equations. And maybe some curl(curl(an E field))?

[mrvlhs]

It's a little hard to distinguish decimal values, multiplications and comas in your videos because of the low resolution. Maybe you could make them more noticeable in the next videos. Please consider that. Thanks :)

[1limonche]

Great! I have understood for the first time what expected value means. Thank you! Great explanation!

[lifeintechnicolour4]

Thank youi so muchhhhh

[sanmathi1]

great work..keep it going !!!!!!!!!!

[khyer123]

THANK YOU! I'm currently taking a class called Probability and Engineering Application with an absolutely awful professor who can't explain anything, and who wrote a book which is just as unhelpful. Thanks for going over this stuff clearly :)

[ismaelOnTheGround]

@khyer123 from uwo ? 

[PoeRilla]

@khyer123 based on what you just saud, we may go to the same school!! lol

[wtube5]

Thank you!

[paulbryanjavier]

Thank you thank you. For people like me who's been done with school 10 years ago... Your videos are truly appreciated! :D Keep it up!

[Ritzoid]

You hit the point home man, great job!

[CogitoErgoCogitoSum]

Time stamp 10:39. Is that right? Zero TIMES a percentage? Zero isnt a value, its a category... right? Zero, one, two "shows up" such and such percentage of the time are categorical. Six has the same percentage but isnt treated the same way. Im confused. These numbers could easily be replaced with red,green,blue,etc.; the fact that they are numerical values doesnt necessarily mean they are values to be used arithmetically.

[cosmomarch]

because you are calculating an "expected value" or "expected score" then you have to take into consideration the numerical values for the "categories".

if the categories were red, green, blue, then you would not be able to calculate an expected value in terms of a number. but since these are numbers it is possible to predict the most likely number by multiplying the score by the probability.

[Sisagirl23]

so great! thx again!

[thefragile900]

It can't get simpler than this.

[qingshuione]

nice,thank you!

[pardes5]

great .... easy to learn... keep it up... thanks