In: Statistics and Probability
Box plot has been explained with an example
C:\Users\Vicky.Crasto\OneDrive - Unilever\Work file\10. Question_solved\770. Descriptive stats for 10 values
A box plot is a graphical summary of the data and to understand the descriptive statistics very easily.
The data is divided into 4 parts.
The first level is the Quartile 1 or Q1, which contains 25% of
the data
The second level is the Quartile 2 or Q2 it contains the 50% of the
data. This point is also called the median.
The third level is the Quartile 3 or Q3 which contains 75% of the
data.
The difference between Q1 and Q3 is called the interquartile range. It is a very useful statistics when the data has an outlier. It acts as a substitute for standard deviation as it is not affected by outliers.
In the box plot the 5 point summary is shown.
The low most mark is the minimum value, next is Q1 , then Q2 followed by Q3 and find the Max value.
Values which are beyond the min and max point are considered to be outliers.
In the box of the box plot the spacing between Q1 , Q2 and Q3 helps us to undrstand the degree of dispersion and also the skewness of the data.
The below box plot shows the weight of 10 men working in factory.
min value = 45.2
Q1 = 47.25
Q2 = 59.25
Q3 - 88
max value = 99.6
There are no outlier.
If you see the position of Q2 line it is placed at the centre of
the box. Indicate that data is skewed.
Since it median value is closer to the min value, the data is
skewed to the right or it is positive skewed.
Additional work as to how the values are derived.