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And welcome back to another class of our course about data science, a complete introduction.

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So we're going to discuss we are going to talk about the basics of statistics and we are going to talk

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about some basic formulas.

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So really basic concepts.

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You'll see it's really, really easy to vote.

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So basically, the three formulas that are going to be covered today would be the median, the mode

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and finally the average or the mean.

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And as you can see, those are pretty simple, but yet really important in statistics.

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So basically, the first thing that we are going to talk about today would be that median and basically

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the median is simply the middle number inside of a deficit.

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So let's take an example right here.

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We have one, two, three, four, eight, nine twenty two.

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In this case, the median will be four, even if it's not the center number in this world, the central

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number means the number between one and twenty two, which would be 11 in this dataset.

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This is the middle number.

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So this is the number that is in the medium well in what is that median here?

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As you can see, it's the exact same thing.

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It's a perfect representation of it.

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So right here we have a dataset and the median will be right there because this is the number that is

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in the center.

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So basically, each time that we have a number that is in the center, no matter how big the dataset

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is, this would be the median.

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So let's say, for example, we have one, two, three, four and one thousand.

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Well, in this small dataset, the median number would be three, even if the average between one and

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five and one thousand would be five hundred.

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But in this case, it's going to be well, the median would be three, because this is the number that

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is in the center.

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So this is for the median.

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The second thing that we are going to talk about today would be the mode.

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The mode basically is a bit different from the median.

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Very simple to understand as well.

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Basically, the mode is the number that will appear the most inside of a dataset.

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It's possible that we have data sets with more than one mode and also it's possible that we have data

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sets with no mode at all.

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So let's say, for example, the dataset right here, which is one, two, three three three four eight

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nine twenty two twenty two, which in this data set, the mood will be three because three appears three

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times in this case.

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And since it's a number that appears the most, this would be our most same thing for twenty two in

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this case.

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Twenty two is not the mode of this data set because it appears three times to be, it appears only two

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times and the number three appears three times.

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And if we didn't have that number three in this case, the mode will be twenty two.

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If like for example, in this dataset we have five numbers and all the numbers appear only one time.

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There is no mode in this case.

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So we have in this that set new model.

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And if for example, we have here three, three, three and we had twenty two, twenty two and twenty

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two, twenty two the average three times.

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In that case the model has been three and twenty two because they appear the same number of times.

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So as you can see in this picture, this represents it really good.

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So basically we have the number 10 right here.

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Thirty here.

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Fifty three.

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Seventy nine.

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So basically the number of seventy appears forty times.

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And this is why this would be the mood of this dataset right here.

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All the other numbers don't appear as much.

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So if we had, for example, 90, that appears as well 40 times and then it would have been as well.

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So we would have had two modes inside of this dataset.

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Finally, the last thing that we are going to talk about today would be the mean.

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And as I said, this is pretty simple to understand.

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Basically, the meaning would be the average of a set of numbers that we have in this case.

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The example is directly here.

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So let's say we have five numbers.

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So the height of some people, basically the mode in this dataset would be there is no more.

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So since everything is the same, the median would be one meter seventy centimeters.

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So basically in this case, one hundred seventy centimeters.

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And finally the average or the mean, the weights, typically it's pretty simple.

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You simply make an addition of all the numbers that we have right here and we'll divide it by the number

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of numbers.

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So in this case, we have five numbers or five entries, so we will divide it by five.

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So the calculation is right here.

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What we have done is pretty simple.

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We made an addition of one hundred fifty one hundred sixty one hundred seventy, one hundred eighty

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and one hundred eighty eight right here.

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So I made a mistake.

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We have a mode.

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It's one hundred eighty because it appears two times that difference.

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And finally the answer would be.

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840 divided by five, because we have right here, we have our five numbers and divided by five, it's

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one hundred sixty eight centimeters.

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So if I make a quick summary, it's pretty simple with this example.

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So first of all, we have the median, which is one hundred seventy centimeters, the mood, which would

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be one hundred eighty centimeters because it appears two times.

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So since it's the number that appears the most, it's our mode.

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And finally our average, which would be one hundred sixty eight centimeters.

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And how we made the calculation, it's pretty simple.

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We simply made an addition of all the numbers that we have here and we divide it by the number of numbers,

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which is five, as you can see, those were the three basic formulas that we talked about.

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So in the next class, we are going to learn some well, some concepts and formulas that are a bit more

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advanced.

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So that's where the glance guys and see our next class.