Statistics: Standard Deviation

[jhiott08]

Thank you so much. Ive been having trouble with getting this cause my professor is Russian and he never explains it with numbers. You probably just saved my ass.

[darkphantom28]

28 professors don't like this guy.

[houdapurple]

@darkphantom28 hahahah yeah ! lol

[megafighterking]

i fukin love u

[Mesosmartical]

I pay $22,000 a year in tuition to learn Stats on Youtube. ugh life!

[BABAMUMBU]

Ihave to calculate a data set with 100 numbers, there are some numbers that are repeated many times, is there a shortcut to input the number of times that a number is repeated in my TI-89 calculator, EX: I input in my TI-89 variance({61, 61, 61, 61, 61, 61 ,61, 63, 63, 63, 63, 63, etc}) is there a symbol to make life easier to repeat the number x amount of time? EX: variance({61(symbol(amount of times to repeat the number)), 63(symbol(amount of times to repeat it)), etc}) ?

[MystyrNile]

@BABAMUMBU You may be able to do something like that with a spreadsheet program on the computer, or something.

[chance20m]

@ion010101 If they're determining s in advance, they are wrong. However, if they're assigning an arbitrary number of standard deviations to set categories (say, any IQ over 2s from the mean is a genius, 2s under is special needs) that is okay, it doesn't change how s is determined in the first place.

The only other thing I can think of is that since IQ scores follow such a well-known curve, the people are skipping steps and just picking 15. I'd have to see what you're looking at.

[SymmetricVortex]

Better than Berkeley lectures, well the statistics one idk about the others o_O

[chance20m]

@ion010101 That's okay, you would say those guys way out there are "x standard deviations from the mean". One of the reasons we use standard deviation in the first place is to determine whether or not a value is "unusual" or not, so a couple guys in a different galaxy don't invalidate the standard deviation at all. Think of sd as a measuring stick calibrated for a specific job. It's only as long or as short as it needs to be.

[vicisrussian]

LEGEND

[likhavel]

how do you know that the bias is removed by subtracting 1 from the population in the denominator?

[chance20m]

@likhavel Dividing by n instead of n-1 will cause the sample varience to underestimate the population varience. If you do the calculation enough times you should see the two spilt more unsing n than if you used n-1. If you want the actual mathematical proof on *why* this is, you 'll need to google it, I don't know.

[MystyrNile]

@likhavel Look up Bessel's correction on Wikipedia.

Imagine you have a population of numbers.

You take just a few numbers from that population.

What if you just so happened to pick some of the smaller of the population?

If you did that, then the average that you got would be biased, because the average you got was BASED ON those small numbers, thus making your average small, too.

Using a smaller denominator makes a larger quotient, enough to remove the bias towards the sample population.

[MrDavidag888]

@ion010101 Those would be considered Outliers and would not be included in the calculation in the first place. They are exceptions to what you would expect... think of the chances of winning the lottery; some do win the lottery, but the probability would be like 1 in a million.

[TwistedPencils]

can you do standard dev and variance for grouped data? Cause that's our focus for grouped data. This is only for single data.

[guitarmessiah95]

That's a sexy calculator.

[JohnBarchard]

@guitarmessiah95 lol trolling

[crizthakidd]

240p we meet again

[joshuamcastle]

24 people are screwed tomorrow...

[SoraXDancingXStar]

I wish your handwriting sucked less.

[robmundo]

@SoraXDancingXStar

Not the easiest to be writing using a computer and probably a mouse?

[MommaoDnA]

Thank you very helpful!

[vDIABETICvHEROv]

soo not taking this in college..screw college all together, military lol

[JohnBarchard]

@vDIABETICvHEROv yeah military!

[vDIABETICvHEROv]

@JohnBarchard f yeah

[Kakashi100000]

ugh learning this in high school is terrible

[theoriginalandrewia]

A wee bit confusing...ah well, that's what happens when you draw on a time limit in a 240p video.

[xxhailybabexx]

Im a freshman & i'm in a math magnet school & we are doing this in research class O.o

[JoshuaRulez1]

U suck jk love u Khan u r the best teacher I every had and that's saying something

[dianasierra123]

My dusty brain's light bulb just lit on! Thank you for your expertise.

[ueyfby31u4bgvfiu31bp]

internet for f***sake.....young generations u lucky baztards

[parag183]

u saved my dream khan...thanks a lot...u r GOD to me...

keep servicing humanity...

[mscairnss]

This 'series' is fabulous for visual learners! Thank you so much for your time in making these informational videos! Well done!

[awesomealishax3]

MAKKES SO MUCH SENSE NOW. THANK YOU <3

[Bapewatch01]

i think, im going to to kill myself... reli, this is too much now... i thort i was the only 1 who doesnt understand this but there are others like me :)

[MrDavidag888]

@Bapewatch01 It's not that hard... go to to Khan Academy's first video on Statistics, learn the terms, then you will know what the symbols mean.... Also, check out UC Berkeley's Statistics 21 course here on youtube. Start from video 1... Very easy

[AnumCanDoIt]

im just as confused as i was before. fuck the woooorld

[ooker777]

look at 16 dislikes and 16 likes in the comment "i hate this" lol

[crustytowel]

holy f**king THANK YOU. been working a real basic st dev problem for 30 mins using tha bullshit my prof gave me and it wasnt working. exam tommorrow im gonna dominate it now

[ishouldbesleeping0]

CSU tuituion $2200

Actually learning Stats in a Youtube Channel.....FREAKING PRICELESS!!!!

[ritesh024]

@ishouldbesleeping0 are you from colorado state university?

[ishouldbesleeping0]

@ritesh024 Negative California State University San Bernardino

[lutwey]

@ishouldbesleeping0 where do you go? im about to transfer and they are asking 3200. hahaha YOUTUBE IS AWESOME!!!

[ishouldbesleeping0]

@lutwey Cal State San Bernardino

[WeAreLions013]

@ishouldbesleeping0 wow!!!!!! that is saying a lot.

[corderomichelle]

@ishouldbesleeping0 lol



[CanEHduh88]

@ishouldbesleeping0 Well if you want to get technical its actually (cost of your computer) + (internet fees) + (electrical bills) =

a hell of a lot more then your tuition

;) ahahah

[Levienkhoma]

@CanEHduh88 OMG the cost of all that is very negligible. This is best value for Youtube. I am totally in love with youtube maths.

[TheSjs92]

@CanEHduh88 Public library = free. :P

But aside from that college is a valuable experience (though the value has gone down over the past several years or so.) and will give you such a degree that will get you in the door for job prospects. It's highly encouraged that anyone that is capable to at least go to a community college use these resources as supplementary, because although these are helpful it's best to have a textbook and work problems out to better learn.

[mynameiskhan26]

Uhm. What does the i mean? And under the sigma, it says i=1. what is that indicating? Please reply :(

[lalwhyumad]

@mynameiskhan26 The i just means the position of the number in your "list". Let's say you have [4 6 2 1]. If i = 1, then X1 = 4. If i=3 then X3 = 2..

[WrathofKhanII]

@mynameiskhan26 Sigma is sum, that whole complicated formula is just the average

[alias4lifee]

@WrathofKhanII nerd.... jk jk :)

[WrathofKhanII]

@alias4lifee Well, seeing as I'm currently in HS Stat... lol

[Melzkewl]

Thanks so much, I think I understand it!!!

[TheSteelArmor]

I am replacing my prof with this guy :)

[FastMovinTrain]

i wish you were my stats prof...

[Jukukiwaiyi2]

still not got that cold sorted out

[sandslash123]

In other words: We are doing root of variance just to get it into the right units presumably that the initial units (not squared) represent the right statistical measurement, thus making variance wrong?

It's all for the intuition of what seems right and wrong?

[hugheshuey]

I thought it made more sense then when my teacher explained it, he was all over the place thank u

[torres0efron]

I think I'm in love

[KKBimmer]

The Khancept, YEA BUDDY

[OrlyDudeGuy]

Khan is the Man

[jumpjlx4]

fuck math

[sgtguy1]

I wish we could ask question if we don't understand anything

[ocgroove]

Very well explained!!! I wish I had you as a tutor when I was an undergrad! :)

[kxmode]

0:58 A population of cows! :P

[pinkmusiicluva]

This really helped me, thanks so much!

[divvy1400yam600]

Circumlocution is the major flaw in Khan's otherwise excellent presentations.

I wish he would take steps to reduce the tedious repitition .

[Ktangsy93]

Take it out the word can't. Keep the word Khan. We Khan do it! keep up the good work!

[JohnnyBankai]

Thank you.

[glendaledgister]

A litte too many deviations from the point that you are explaining... a student trying to understand only needs you to go to the heart of the matter... the rest can wait until we become expert at the basic.. But thanks anyway..

[sirries1]

I love you Khan. OMG I'm flunking my Statistic class but maybe there is hope for me. Yay!

[espencerrrr]

you are the best everytime.

[hotLink87]

U really make it UNDERSTANDABLE.... thanks a lot i have a Test tomorrow and im not gonna fail thanks to this videos! cheers man!

[TheExterminator123]

Great videos this guy is awesome saved my life lol

[ahmad1142]

wtf. this didnt make any sense at all.



[dudecoolname]

@ahmad1142 If you went straight to this video you won't figure it out. Go to his channel and watch the 4 videos that came before this one and you will understand perfectly.

[sweetxXxgirl0o0o0]

fml im failing

[lovorlie]

yeah... not so good for an alg 2 student in highschool, whose teacher cant really teach..... fml lol

[tenseman08]

i'm studying this subject in one night.. for the exam tommorow..from scratch..god help me!!

[Jesse639]

Im screwed for tomorrow's exam x__x

[krheine]

thanks so much :) u helped me allot with this tutorial :) 

[gopipatel23]

Soo helpful! Thank you!

[lild5037]

i hate this

[MsNJohnson]

Amazing!!!

[grenePnaimoskee2]

3000 level statistics? That's hardcore intense.

[LeBadman]

@grenePnaimoskee2 It's over 9000!!!

[FarhanC99]

SUBSCRIBED!

[theplayboy92]

Very Helpful.



[mango119]

Thank you

[jazz77ol]

I am still a little confuse about the difference between standard deviation and variance.

[jazz77ol]

@jazz77ol

I just answered myself. Standard deviation is pretty much the same thing as variance Except it is the square root value of The variance. Further to calculate the variance one would uses the whole population value where the standard deviation 'requires' just the sample value.

I thought someone else may have the same confusion and this might help.

[RicoleNichie]

x with a line on top is x bar

[DawnBreaker1100]

@RicoleNichie Yes, but not many beginner people get that.

[nhudgins]

You are the man!

[blueknarf]

Awesome explantation!!!

[mizzannie001]

waaaaah

[vishalsinghnumerouno]

i wish i had these videos when i was taking stats.

[Ho3slutty]

man you are awesome. I wish u were my professor. Mine writes horrible and teaches verrryyy poorly

[anidethiopia]

tnx

[welshboygreg]

You write better with a mouse than I do with a pen.

[jinwon521]

@welshboygreg he is actually using a tablet... i think

[GlowMagik]

25 Samples of 3 observations. To work out the standard deviation of the whole thing, do i sum the standard deviation of each sample? or include 75 additions in the variance equation?

I suck at stats, any help would be much appreciated, honest :)

[davmth1]

Ive been watching these videos for few years before exams.. thanks for making em m8!

[sandradeethmamma]

I just want to thank you...I have learned more from you in 13 minutes than I have learned for a week's worth of class. ;0) Thanks again!!!

[mrsirsouth]

I'm concerned... why do I come up with a different answer in excel?

[lllUSlll]

do it on a whiteboard :o

[MoonKittenJD]

"Lets calculate a bunch!"

lmao i wonder how many "standard deviations from the mean of the population" you'd have to be to get excited when he says that.

[whiteoddessey]

Very Clear explanation. Stat is fun again. Thank you VERY x100 much!!!

[Thecrazyjords]

Many thanks!

[dilibau]

I Khan has cheeze? :D

In other news, 6 people are deviant from the standard common sense

[mrhnm]

Why do they square the difference between the mean and the points instead of absolute valueing it?

[lilababy76]

@mrhnm my psych professor explained to us last week that this happens because making the most extreme values stand out even more, is generally desirable. this of course goes for psychology. i don't know if this is his personal estimation or a universal truth, but anyway i hope it helps :/

[aida1887]

The Best!!!!! Thanks =)

[Mr46ser]

Yes we Khan!!!

[irfanulhaq1]

y dont u explain it properly

[Spydiggity]

this video needs a *record scratch* sound effect @12:27

[renj3000]

i like the way you teach

[archiemedes42]

How did YouTube let you go to 13 minutes back in January 2009??

[kingofbad111]

You are the best, i suddenly started my Master's in computer engineering and was i bout to withdrow, after finding what this guy is teaching in math and statistics i had a hop again, u are amazing man, truly amazing by all means, keep it simple like u r doing, u made math truly to be fun.

[niebianca]

Thank you...I'm getting crazy with this stuff and you help me a lot

[lubuuko]

phew problem solved, Thank you

[maggie5656]

thanks so much. it helps a lot

[19Laraholic]

THIS CAN HELP FOR MY PROJECT!!!!THANKS!!

[Faithierox]

Your videos are very helpful! I cannnot understand my instructor and am passing thanks to your tutorials! Thank you!

[jiffync]

Well deserved thumbs up, great breakdown and technique. TY

[ksaloverksa]

Thanks, I really appreciate your works. Keep it going!

[babiixbluexox]

wow i actually understand it..

thank you so much!

[msnoah]

Great step by step

Thanks!!!!!!

[msnoah]

I am taking my 1st and last class in statistics.

This instructor breaks it down and explains clearly

I wish my professor had the same teaching techniques

[IdiosyncraticChild]

Now my parents are gonna love me. xD

[Megumix33]

wow amazing ! the in build calculator in his com looks so real O.O i wish i had one as well heheh

[TheAustiniho]

I am training to be a maths teacher..... My students will be directed here!

[CoasterChick22]

thank you for making my life tons easier!

[TheAlex511]

Your videos are the best I have used you for about 2 years! Better than my college profs.

Thanks

[deen2dam]

very good explanation. I feels that i shouldn't go to my statistics lectures. because i can understand those stuffs better, than in lectures. thanks. keep up your good work. Cheers.

[Taowhr]

"I will see you in the next video, oh wait..." Oh Sal...

[wolfadamwolf]

thanks

[EricEthridge1]

Your videos have help me so much. I am no math person, beyond basic algebra. But with your help I am actually learning some of the more advanced math - such as statistics). Thank you.

[daislytube]

You are making it easier to learn so many stuff at maths, so biggg thankksss for thattt, however you are writing the things so bad pleasseee just do something for your writing, please please please.

[CurlyVogel]

*bows* you are the master of math!

[ThaOriginalGangsta77]

yo i know majority of statistics..but can u do a calculation regarding a standard deviation of NPV. it should be a coefficient of a variance squared? thanks bro.

[SoSyNiKaL]

You're fantastic!

[codekiln]

Kahn - thank you! My favorite morning ritual for the last couple months has been eating steel-cut oatmeal, drinking coffee, and watching one of your videos. It wakes the brain up in a painless, entertaining way. I'm a piano performance major who once considered being a math major, but never went beyond Calc 3. Having your videos makes me feel like I'm just connected enough to that world I love!

[vladimirrngs]

thank you, Khan! with you, i understand these concepts so much better than a lot of times in my mother tongue. pls keep going. you've promised geometric and harmonic mean in the 1st video) and that's exactly what i need to brush up.

[IRAQrecords]

fan-fuckin-tastic

thankyou thankyou thankyou

[3runrob]

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[3runrob]

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[3runrob]

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[naziasherif]

damn this video has made sd more complicated..

[youmils03]

Standard deviation is not easy to grasp. I took it as a freshman and had a hell of a lot of trouble with it. It's super confusing and takes a lot of practice. But by the end of the course, students start to catch on to the idea of it. "standard deviation = spread"

[qaseem65]

Good! Khan

[Anarchisttttt]

You're THE MAN SAL!

[koolmayyn]

you are a top geezer thanks alot mate

[telespence]

@koolmayyn Ha! Brits... Love y'all

[parthsna]

I bet Sal was one of those dudes in university who all the people would come to for help right before exams. And that is why he breaks it down so well for beginners because those dudes who came to him right before the exam did not know anything. Lol.

[coxfox10]

I'm a systems engineer in a 3000 level statistics class with a professor who can barely speak English. I have never taken a statistics class before so I find it rather difficult but I learn more from these videos than my prof. This guy can teach it so much better because he knows how to break it down on a beginners level. Thank you Khan!

[tzikidusha]

@coxfox10 are you studying in London? because I find myself in the same situation :)) anyway thanks for the uploads!

[Losuol]

@coxfox10 That's the thing! Most profs just get paid to tell you about the information so they just spew out the stuff from the text. This guy builds it up from a beginners level which gives him more flexibility later on since once students grasp the basics they can easily learn the later material.

[samathalev]

you know what your the best. I really love all your videos. Honest and they really help me a lot hope youl never stop what you are doing. Your really helping a lot of people

[ufo8mykat]

I can do it now! Coooooool. Thank you! How fun!

[bontea]

how do you know when to divide by the population (n) or n-1?

[TrickyJumba]

n is used for the whole data

n-1 is used when you're dealing with the SaMPLE of a data

[lisaisbizness]

Excellent!!