Name: 中心限界定理 (Central limit theorem)
Uploaded: 2021-01-14T09:14:29.000Z
Duration: 3 min 42 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

the central limit serum is one of the most important concepts in statistics.

The reason for this is the unmatched practical application of the serum.

The first thing you want to do is start taking out some sets from the data set.

Or as statisticians call it, you start sampling it.

This would allow you to get a better idea of how the entire data set is made.

Once you have taken a sufficient number of samples and then calculated, the mean of each sample will be able to apply the central limit serum, no matter the distribution of the entire data set by no meal uniform or another one.

The means of the samples you took from the entire data set will approximate a normal distribution.

The more samples you extract and the bigger they are, the closer to a normal distribution.

Their distribution will have the same mean as the original data set and in end times smaller variance where n is the size of your samples you took from the data set.

Let's confirm the theorem with an example.

We have prepared 960 random numbers from 1 to 1000.

This is their frequency distribution, so you are sure that they are randomly picked.

The mean of this data set is 489 and it's variance is 82,805.

Let's extract 30 random samples out of the data set, each consisting of 25 numbers.

Remember when we said that the sample should be sufficiently large?

A common rule of thumb is that the sample should be bigger than 25 observations.

The bigger the sample size, the better the results you'll get.

Now we're going to calculate their means and plot them once again.

It looks approximately normally distributed, doesn't it?

Let's check if the other part of the theorem was right.

The mean of our newly acquired data set is 492 while its variants 3171 did we expect these numbers We anticipated a mean of 489 at a variance of 82,805 divided by 25.

Well, when dealing with such big numbers, we almost get the mean right.

And the variance was not that far off either.

In the next few lectures, you will learn how to statistically confirm whether such small differences are close enough to the actual result.

So we have learned the main idea behind the central limit.

Their, um the key takeaway from this lesson is that the number of samples taken tends towards infinity.

The distribution of the means start approximating a normal distribution.

If your data set was made up of millions of values and you could afford to sample just a tiny bit of them, we could be assuming normally distributed data almost all the time.

And that's extremely helpful, as you will see later on.

 Okay, Thanks for watching form or videos like this one. 

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中心限界定理 (Central limit theorem)

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