Introduction to the Normal Distribution

[strawberryswift]

Great Introduction. :)



[THE16THPHANTOM]

this is still super difficult and its the most important important one.

[Saronaist]

LOL. this is too much for me. Maybe i should switch to the videos of Normal Distribution problems because I know nothing about Calculus YET!

[pradeepknal]

thanks a ton for all the teachers and staff team at Khan Academy!

[DivinityFaith]

I believe you are somewhere to the right of the normal distribution graph, probably somewhere near 6.9 billion, if we were to make such a graph for "helpful people".

[brandex24]

I doubt i am the first person to comment on this but your comment on all of the atoms arranging themselves so that you can fall through your chair is actually not unlikely its impossible because of the electromagnetic forces between the electrons repelling one another. Not being a stickler im just bored haha

[pleasepardonyourself]

@brandex24 according to quantum mechanics there is a small chance that it can happen. very very very very very small. but still a probability nonetheless

[dealerbuttons]

at 16:12 I think it's e^(x+5/200)² instead of e^(x+5/100)² :)

[Br3nD0g]

When i watched this video and finally understood the normal distribution, my atoms re-arranged themselves and i fell through my seat....

[BeGunNer]

Is the Cumulative Distribution Function a Logistic Function with carrying capacity 100% or does it just look like one? I am not sure, because it seems to copy the typical shape, but I can conjure up no substantiation as for why it should be that way.

[MrAgoose]

I have a question that i need help with. The question goes...."The scores on a statistics examination are normally distributed with a mean of 60 and a standard deviation of 10. Calculate the following probabilities:

A. The lielihood that scores will be less than 50.

My question is for the z- score ...would it be (z--1) thus P(z<1) + .3413, or would I have to subtract that from .5?

[OddsDiva]

Sal, you are so awesome to open up this world of knowledge to anyone interested in learning. Thank you!

[MasterThief1324]

1:35-2:00: In a probability distribution of a continous variable, shown by the normal distribution curve, is it impossible, not correct, or simply not the job of the normal distribution curve to approximate the probability of obtaining a discrete integer value (i.e., a number on the x-axis)?

[NaserNazary]

Also I find it very helpful thanks khanacademy.

where can I fnd more videos?

[mattstiehl]

Wonderful video. Loved it, thaks a lot!

[V2PRC]

Help! Can't download the xls files!

[hardtrancelover92]

Thank you so much for uploading this video! I'm in a high school Algebra 3/Statistics class right now, and my teacher didn't explain the normal distribution concept very clearly. I'm definitely using your video to help prepare myself for the final exam! :D

[Pmarz15]

are you the guy from ancient aliens?

[sasamuraki]

wow, that part of linking normal distri to 'nothing is impossible, but the probability matters' is awesome.. deep...

[muzic29]

thanks so much for this.

[xtruder02]

I LOVE YOUR VIDEOS ª!!!!! KEEP DOING MORE PLEASE :)

[kukujos]

I am a political science major. I should not go deeper on this stuff. I can argue all my life about why me not taking Statistics class but I need it to graduate. So thank you! I am very very thankful you made this.

[aer9998]

trappezzoid? naah your gud

[MrPlender]

Call me stupid but why do you have to use the cumulative distribution function to work out the area under the curve? Why not just evaluate it on the normal distribution as it is?

[xtruder02]

@MrPlender BECAUSE you do not have an area x>0 , you will not get nothing... if you just evaluate the function, that means nothing...

[sajn0001]

Thank you very much Mr Khan.

The best tutorial ever.

[haloapa]

OMG! I am so blessed to have the Graphic Calculator (GC) ! I just need to press and i can get the answer. I am using TI-84 silver edition GC

[haloapa]

AH! I found this video! great!

[captainbeatle]

You are Jesus.

[captainbeatle]

But mistake at 15:52, it's not sigma^2, just sigma, since the exponent's already outside the parentheses.

[NCAD]

terrible demonstration

[sumitece87]

Thanks Sal... Can u make some videos on Birth and Death Processes and markov chain and series. thanks...

[Dermiitti]

Thanks. Well explained!

[mishkail01]

Hi there.

It is helping me to grasp the basics. I wonder if you have any plans to explain this in SPSS format. Universities have this nasty habit to stuff stats down your throat even if you do not want to become a statistician nor a researcher. Your KISS approach is appreciated.

[mujimax007]

You are fabulous. By the way, at which college or university do you teach. Thank you.

[mohit01985]

great work! thank you.

[TajikThunderstorm]

This tutorial reduced my fears to zero, feel a lot better now!

[masoodghasemzadeh]

Excellent tutorial. Simple and clear.

Just as feedback : It's gonna be perfect if you speak a bit slowly, specially for non-english viewers.

[talentokie]

I wish i had youtube when I was in school...wud have learned a lot of things better.

[salemali83]

Can you post video in Probability about Moment & Correlation please

[DanMan7997]

Hey Sal, great series so far on statistics. Hope to see more videos in this series soon! I'd especially like to see you continue with normal distributions with some examples of when it's appropriate to assume a normal distribution and when it isn't. I think that will be a big help for people that want to apply the normal distribution to some particular phenomena they are studying, or scrutinize someone else's application of it. Thanks!!!

[vkgoku2012]

If I wanted to know how much worse my eye sight is getting.

[dobromir2102]

Hi guys,

I find these videos very helpful. Even though, I am a PhD student, it is a nice refreshment of Statistics. Does anybody know if there are more of the videos on Statistics from Khan Academy. Khan mentions in these video another lecture on the Z-score, but I do not see any on youtube and neither his website. Thanks in advance. Dobromir

[MrAwesomeAsian22]

@dobromir2102 hello Dobromir, it is 2 years since you have seen this video, but i hope you still have your positive attitude for Statistics! anyways, to find the video you are looking for press Ctrl and f, and type in the keyword you wish to search for. In your case, i used standard deviation as my key words, and it brought me to the statistics section. In the section there is an intro to normal distribution. under that, you have z-score. Hope i helped! reply if you have any questions.

-Wasfi

[Jakers2009]

Sal... super video by thw way... Dont mean to get involved but maybe this guy should do some research into the example you said about your atoms falling through a chair if he wants an extreme example... What I am interested in is you continuing this idea into the central limit theorem and also some of the financial examples you said you may do.... I am starting to see how this could be used to value options or the intrisic value of an financial instrument....

[CogitoErgoCogitoSum]

Human height is a normal distribution? So, the probability of a human having a height less than or equal to zero is actually a defined real positive value? And yet is impossible at the same time. It makes the normal distribution confusing and meaningless, essentially.

[khanacademy]

the normal distribution is a class of distributions that have the same basic shape but different means and std deviations. Human height is probably close to a normal distribution with the mean around 5'6 (somewhere in between men and women average).

[CogitoErgoCogitoSum]

I dont think you get what I was saying. Your response might be a valid response, but it neither constitutes an answer nor is it even relevant to what I said.

[honeybbqgrundle]

It's an approximation to the probability, and it's usually a very good one. The probability you speak of is obviously 0, and using the normal curve on a height range so far from the average (like 22 SDs) would give an unbelievably small probability. What's the problem with that?

If you want the exact probability for a height range, you're welcome to go measure every person on Earth. Most people would be satisfied with using the normal curve.

[CogitoErgoCogitoSum]

@khanacademy Your response in no way reflects my original post or its concerns.

[tenshady]

Thank you very much Khan,

Wishing U & ur Family

Best of Health & Happiness

[Person514cs]

That's very interesting

[wwwdotLPdotorg]

Great video, it is helping me prepare for the AP.

[AlbiCollier]

what level is this lesson??? please don't say high school!!!

[Tehcarp]

If you did statistics in high school, this might come up.

Don't worry though, if you spend more than half an hour on it, or work backwards in the maths you need to understand (try an elementary stats textbook from your local library) this will quickly come under your power to manipulate.

Watch some more videos!

[wwwdotLPdotorg]

AlbiCollier

Most students in high school (or at least mine and my cousin's) don't take statistics since it is mainly a college course. They offer the AP statistics exam for high school students who want to get ahead.

[djkadirtube]

best channel ever.

[norwayte]

You have the gift.