Boxplots
Introduction of Boxplots in statistics
Registiraion No: FA18-BSE-029-A
What is boxplot
• A Boxplot also called as a box-and-whisker diagram is a graphical
version of statistical data based on a minimum value, maximum
value, First Quartile (Q1), Third Quartile (Q3), and median. A
“Boxplot” or Graph looks like a Rectangle with lines extending
from the top and bottom.
How to make a Boxplot
five number summary
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Write the data in order if it is not in order
Find the median of data
The median divides the data into two halves Q1 and Q3.
find the lowest value.
Find the highest value
How to draw a Boxplot
• Draw a horizontal axis that includes the maximum and minimum values of
data set.
• Draw a box with vertical sides with Q1 and Q3 and draw a vertical lines
through the medium
• Draw a line from the minimum data value to the left side of the box and a
line from the maximum data value to the right side of the box
Interquartile Range
• The interquartile range defines the difference between the third and the first
quartile.
• First Quartile is denoted by Q1 known as the lower quartile and Q3 known
as upper quartile
• Interquartile range = Upper Quartile – Lower Quartile = Q3 – Q1
Difference between exploratory data and
traditional data
Exploratory data analysis
• Stem and leaf plot
• Boxplot
• Median
• Interquartile range
Traditional data anylysis
• Frequency Distribution
• Histogram
• Mean
• Standard Deviation