Machine Learning - Data Description - Boxplot with Five Number Summary

In this video we are discussing box plot with five number summary

A box plot is a graph of data set obtained by drawing a horizontal line from the minimum

data to the value Q1 and drawing a horizontal line from Q3 to the maximum data value

Here Q1, Q1, they are nothing but quartile 1 and quartile 3

And drawing a box whose vertical sides pass the number. through Q1 and Q3 with a vertical line inside the box appearing through the median or Q2

So, this is the Q2 will be known as the second quartile can also be called as a median

So a box plot can be used to graphically represent the data set and these plots involve

five specific values. So the first one is the lowest value of the data set, that is the minimum

we are having the first quartile then the median also can be called as Q2 second quartile Then we are having the third quartile Q3 and the highest value of the data set that is the maximum

These values are called a five number summary of the dataset. I think to make the conception clear, we require one example to explain

Let us suppose we are having one set of data on which we are supposed to draw a box plot

So, the data set is 89 47 164 in this way we're having this set of data and this data

is not obviously shorted. Construct a box plot for the data. So, arrange the data, there is a step number one, arrange the data in the order

So, from the lowest value to the maximum value, we have arranged all this data in the ascending order

Now step two, find the median. We know that here we are having 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 data

So, 10 is even. So I cannot find the middle most values In that case I shall be taking the average of the fifth and sixth value so 1 2 3 4 5 so 78 and 89 that average will be the respective median

also will be represented by Q2 or the second quartile so now we are going to find

the Q1 so here it is Q1 is equal to 47 what is the median here that is 83.5 so

83.5 is falling here so in this particular particular set of data calculate its median value. So, now we are getting this 47 as the

middlemost one. So Q1 is equal to 47. Now we are trying to find out the Q3. So here Q3

is equal to 164. How did I get this one? So 83.5 is the median. So 83.5 will be

lying here. So here in this upper part we are having 1, 2, 3, 4, 5 data. So take the middle most

I am taking this one as 164. So we have got the value of Q1 Q2 and Q3 And draw a scale for the for the data on the X axis And step six is that locate the lowest value we know the lowest value what is the lowest value here that is a 30 q1 already we have calculated

that is 47 median that is our q2 that is 83.5 and then q3 already we have calculated that one

has 164 and the highest value of the scale and that is nothing but 296 draw a box

around Q1 and Q3 draw a vertical line through the median and connect the upper value and

the lower value to the box. So here we are connecting this upper, the lower value to the box and upper value to the box

And here we are drawing one box from Q1 to Q3 and we are drawing one vertical line

in the across this box for our Q2. So Q1, Q2, Q3, there is the highest value, there is the lowest value

So, in this way, we have shown you that how this box plot can be done using five numbers

Thanks for watching this video