Random variables | Probability and Statistics | Khan Academy

[@Barnekkid]

Why didn't they explain it this way in school? No, instead they turned it into some great big effing mystery until three fourths of the class lost interest.

[@reinforcer9000]

you didn't get it back then cuz you didn't have interest in it. you get it now because you're prepared and interested in it, which is evident in you searching for it on youtube. I'm willing to bet both instructions were more or less similar.

[@hambonefakenamington69]

@@reinforcer9000 wow that makes sense

[@andrii5054]

@@reinforcer9000 That's not true, I've just heard a lecture on random variables. The instructor hasn't given us a single example, just abstract definitions. On the other hand, Khan's video has taught me the intuition in 5 minutes.

[@TheLynLyn57]

@@reinforcer9000 Wrong.

[@manas1743]

Because, most probably ,they didn't know it that well themselves.

[@WateryIce54321]

Well, we're at a high enough level at this point. I'm sure others can agree by now when I say - looking forward to another great semester with you Sal. In Calculus 1 you were my backup teacher. But, ever since multi dimensional Calculus its like my actual professors are the backup. Truly, I envy your ability to explain topics so clearly.

[@pranavjain9799]

best comment ever

[@WateryIce54321]

@University Every 2 years I find a use for the binomial probability calculator and still eagerly await a real-world problem that justifies years of memorizing calculus formulas alongside this random variable magic.

[@WateryIce54321]

@University Oop, sorry! A less critical view - you're challenging yourself to think in different ways, working on your ability to memorize things, and it leaves more options open for the future! There's engineering and physics problems in the world being modeled with these tools.

[@ea1766]

@@WateryIce54321How you doing now pal?

[@rektoman620]

@@ea1766 he deleted his youtube probably

[@brco2003]

A lot of people struggle with probability because they skip over this introductory concept, dismissing it as basic and taking it for granted. However, a solid grasp of this concept will pay dividends when one encounters the core concepts of probability theory and statistics. Thanks, Sal!

[@sreeharshaparuchuri6115]

hmmm, interesting. thanks!

[@abhirawat1889]

I have logged in just to say "thank you for the wonderful lecture".

[@OrbitUnraveler]

Yes indeed its actually helpful

[@mayurp3958]

How I understand randomness is that it's a measure of knowing that an event will occur but being unsure about its outcome. Hence, we use random variables to map out (or quantify) the outcomes of those random events.

[@jessicafessler]

you're literally the only reason why I'm managing to get through my business degree

[@ishita2727]

Where you from?

[@fuzzywuzzyangel7646]

You're literally my life saver through college.

[@priyanshuyadav4438]

in college?? we have this in high school in India

[@conversation2581]

@@priyanshuyadav4438 we do to. But you need to understand the basics, before you can start solving complex examples that come in college or university

[@w0nnafight]

@@priyanshuyadav4438 who cares about india

[@BoZhaoengineering]

Khan academy is like a video Wikipedia in academic.

[@anshpradhan1954]

Voice is too dope 🔥🔥🔥

[@Fennecfox10]

A random variable is the same an event? My book tends to use capital X as 'random variable' for probability problems and they use capital A, B, C for Events, subsets of a sample space.Furthermore, capital omega is random space for probability and sample space when discussing events. Sorry if I made poor distinction, but I don't understand why they is a distinction. Perhaps a random variable is a specific kind of Event where it is a 'real valued function, and similarily for random space being a type of sample space.

[@CathyZhang]

Random variables are functions that map events to the real number line.

[@chadchad6531]

yes. I'd add to this that by events, we usually mean a text or sth. I used to think that random variables looks sth like this: when rolling a dice the domain={1,2,3,4,5,6}, and the value of a given point is how many times we rolled the given number. NO!! Random variable looks like this- a random point in the domain is "rolling a 6" and you ASSIGN a 6 to that. This is what I didn't understand, just writing it down differently if someone happened to still not get it.

[@DrCycotic]

I am so glad you exist. Thanks for such a nice and clean explanation

[@aregayteklay1267]

very impressive explanation

[@selvam5788]

why do we need random variable in first place?

[@trishnasingh6288]

It's part of probability

[@kamolaablazova8444]

Hello, I always listen to your lessons, I like your speech, you explain the lesson, Please send me simpler textbooks on probability theory and mathematical statistics, from Uzbekistan, teacher Kamola

[@djganit]

Very good explanation

[@MindfulSapient]

Hi! Is this the engineering level Probability and statistics course? I need a place to revise all my engineering mathematics courses including differential and integral calculus, multivariable calculus, linear algebra, differential equations, probability and random variables, numerical methods. Kindly let me know if the maths section here on Khan Academy covers these courses.

[@danielcohenemail]

if your too dumb to go on his website and check the topics yourself then your prob not cut off for all that math

[@mechickenburp4927]

​@@danielcohenemailthats absolutely not too brother, dont be so quick to judge. People much smarter than us have discovered much more mathemtical formulas without ever using technology. We never know anyone's condition but instead should motivate each other to keep pursuing knowledge

[@11-berkeleyroyyuriahkelly89]

what my teacher taught us is this ex. Number of tails in tossing a coin thrice ans. {0, 1, 2, 3}

[@KeyserTheRedBeard]

excellent video Khan Academy. I smashed the thumbs up on your video. Maintain up the solid work.

[@pillsberrydoughboy4542]

him shaking the mouse like that is making me nervous irl

[@helenpark175]

Better than my uni prof

[@neenaji1]

The question is about variables. We would say that “height” is a variable. In my mind, “height” does not just represent different values, like 2, 45, or 75. It represents values + units: 2 feet, 45 feet, or 75 feet. However, when we work with variables mathematically, I believe that we think of them as solely representing values / numbers. For example, we will say statements such as: height = 2 weight = height + 4 weight = 6 It seems confusing to me to have to think about variables in 2 different ways. Could you explain if I’m thinking correctly? How do you recommend thinking about variables so that I can do statistics most effectively? Please reply. Thank you

[@Tubemaster32]

"height" is not a variable but a geometrical concept a variable in math simply stands for anything, it is a placeholder variables can be anything, so you can assign some value with a unit or way more complex things, to a single variable think of variables as a placeholder that allow you to generalize a problem's parameters, so you can provide a more purposeful solution. The variable does represent every/any element out of a given set. They are very handy.

[@MateMafia88]

what software is he used to write and explain the presentation?

[@haneyguitarinstruction6260]

This is THE holy grail to trading

[@vladimirprotein3275]

Khan Academy to the rescue!!

[@FatCat-lr2yq]

What a fruitful topic

[@pedrogaleano6722]

Very clear explanation! Thank you very much

[@balakurna8336]

Let A and B be disjoint events and such that p(A)>0 and p(B)>0 are they dependent or independent??

[@shrutimanimegalai3541]

As they are disjoint, I'll guess they are independent.

[@balakurna8336]

@@shrutimanimegalai3541 thanks very early 👍😊

[@poornimas620]

please upload problems related to it and discrete probability distribution function

[@nakulsharma748]

poornima please contact to me nakul_vats_052 insta id , i`ve no ida about that please help me

[@ceonchoga]

Nice one

[@hughjazz4736]

I should just give my tuition to you

[@cashele]

lmaooo right! he's the only one actually teaching us!

[@ghaith99000]

what is the difference between random variables and events?

[@shrutimanimegalai3541]

I'll try to explain using the first example. Here the event is the coin falling heads or tails. The random variable is the value you assign to the event before it happens, using a function.

[@jonathanmulugeta6807]

thanks

[@OrbitUnraveler]

thanks !

[@Rocks740]

Example mixed Random Variable

[@victorreloadedCHANEL]

I don't understand one thing: If you see random variable as function from sample space into Real number , the first example is okay , but how about the second one ? What would be the function there? It seems as sometimes random variables might be seen as the experiment itself ... like in the second example.. I hope I have made myself clear .. Thank you

[@chuchucat7387]

A random variable can be defined as a function of 1 or more other random variables. This is what he was illustrating with the variable Y. Y is defined as sum(X_i) for i = 1,...,7. There is a whole algebra of random variables that lets us understand functions of random variables as random variables themselves. The case illustrated here is very well understood. X is what we call a Bernoulli random variable and Y is a binomial random variable.

[@lolvivo8783]

@@chuchucat7387 How different is random variable from sample space? I think they are both same but otherwise they wouldnt have been named different.

[@chuchucat7387]

@@lolvivo8783 the sample space is the set of values a random variable can take. Essentially, It is a property of a random variable.

[@mosels9339]

I liked this video. it's so helpful

[@schannerashid89]

So the random variable is similiar to substitution?

[@FilmBuffBros]

Sooo confusing. What do dice have to do with coin flips? So many undefined terms too.

[@darwinvinci7744]

Nothing, that's the point!

[@malteeaser101]

Did it make sense to find the expected value of X when it is assigned by the first method, where you arbitrarily choose random numbers to enumerate heads and tails?

[@arbertmateotambong2691]

Very helpful this video..

[@mirueofblackdesertonline2504]

not clear to my current situation, maybe i dont personally take this as serious as my prof. What i want is direct lesson ( formulas, examples, solution, discussion on how to get this and etc) somehow i dont find this helpful but tnx

[@mhlee6739]

Rolling 7 dice, why not less than 42 but 30?? Somebody help me

[@anirudhkannan9]

Arbitrary example. Can be less than 42 as well.

[@SivaKumar-rv1nn]

Thankyou sir

[@jagritichanda982]

I'm confused. The number should be Y

[@krishnakrmahto97]

how is a random process defined? on the basis of outcomes?

[@shohidul-j2w]

it is important vedio

[@harshitkumar4964]

wasted 3 hrs watching videos and here I get it all and this was 11years ago lol

[@juanpablodt]

My teacher used half a class to teach this and no one unterstood anything. He should have just put this video and it would have been way clearer.

[@barjees7430]

Are you probably the noted anatomist? 😳

[@dollydread8274]

I still dont get it. Lmao

[@Marco85111]

stupid spongebob profile picture

[@dollydread8274]

Hugh Jass , stupid person

[@Marco85111]

@@dollydread8274 hehe

[@hrithicksen3644]

Sad to see

[@danilomenoli]

Me too, bro, LOL

[@alakumar4480]

how about non-random variable ? anyone can explain ?

[@AForAsh]

eg for non-random variables - Flavour topping a customer chooses, ethnicity of customers, mode of payment etc. These are non-numeric values and there is no randomness in it and hence non-random variable. Please do correct if I am wrong.

[@Myndir]

"Non-random variables" are just "variables". Random variables aren't really variables, but functions.

[@aybaws]

Are these “random variables” in the room with us right now?

[@JeffreyNuccio-gd4gz]

why couldn't you use a more digestible example of random variable? WHy sum of 7 dice? why not sum of 2 dice?

[@mayssa8790]

tomorrow is my exam wish me luck

[@raflalink]

Question, that has nothing to do whith the subject. What software do you use to write?!?!?

[@nazltel4794]

help

[@simplypevey5278]

Can you teach at my school in every class I have for math you literally teach me everything my teachers can't explain anything clearly I took Stats in senior year of Highschool and that teacher was better then my senior year of college SMH

[@fayolamaulida1663]

Thank you so much!

[@nakulsharma748]

hey please gie me overview of this theory please help me

[@jouzamujtaba7262]

Done

[@yashwantsingh5328]

how to find expectation of reciprocal of random variable

[@sakhafadilah4037]

gg bang

[@user-gi8fs6xl5o]

I absolutely dont like the black bg

[@pajeetsingh]

upward face lol

[@davedavesnothereman2515]

Be easy to learn if your voice didn't put people to sleep

[@Pages_Perfected]

so if i watched this am i going to get a 100 ?

[@w0nnafight]

sure why not

[@SainathKrishnamurthy]

six

[@atiqasafdar9103]

Its not so clear 😑😤

[@nazltel4794]

İ want turkish video

[@nazltel4794]

+cevelry I understand turkish . how the learn english ?

[@syed5867]

Explain in hindi

[@ganeshvalsalasanal4337]

please stop shaking the pointer all the time

[@abhishekadhikari6469]

Please talk hindi

[@stephenprice3357]

i always lose interest while watching khan academy