Box plot is basically used to identify the outliers(extreme large or small values) in the data set. Box plot is graphical display it provides five types of information about the data set i’e minimum value, maximum value, median, lower quartile and upper quartile. This takes us to a little statistics part.

Note: The horizontal lines are called Whiskers.

Information that can be obtained from Boxplot

• If the median is close to the center of the box, the distribution of the data values will be approximately symmetrical.
• If the median is to the left of the center of the box, the distribution of the data values will be positively skewed.
• If the median is to the right of the center of the box, the distribution of the data values will be negatively skewed.
• If the whiskers are approximately the same length, the distribution of the data values will be approximately symmetrical.
• If the right whisker is longer than the left whisker, the distribution of the data values will be positively skewed.
• If the left whisker is longer than the right whisker, the distribution of the data values will be negatively skewed

Notice here the outliers are represented by a small circle.