Box Plots
• Are a visual representation of the median and quartiles of a data. Things required
to draw a box plot - 1. minimum value
2. Lower quartile
3. median
4. upper quartile
5. maximum value
Draw a box plot for these numbers:
Q: 9, 10, 10, 12, 13, 14, 17, 18, 19, 21, 21
• 9, 10, 10, 12, 13, 14, 17, 18, 19, 21, 21
- The Maximum - 21 and minimum - 9, mark them with a small and short vertical
line.
• The numbers are already in order so the minimum and maximum numbers can be
easily read off as 9 and 21, and the middle number (median) can be read as 14. 9,
10, 10, 12, 13, 14, 17, 18, 19, 21, 21
As 14 is in the middle, draw a line on the box plot graph at number 14.
• Lower quartile: WILL ALWAYS BE BELOW THE MEDIAN. Hence, to find that
out, have to look at the lower half of the data (in range of 9-14). Again, Apply the
median method. (Start cancelling numbers before the middle median - 14). 9,10, 10,
12, 13, Therefore, the lower quartile (LQ) is 10.
• Are a visual representation of the median and quartiles of a data. Things required
to draw a box plot - 1. minimum value
2. Lower quartile
3. median
4. upper quartile
5. maximum value
Draw a box plot for these numbers:
Q: 9, 10, 10, 12, 13, 14, 17, 18, 19, 21, 21
• 9, 10, 10, 12, 13, 14, 17, 18, 19, 21, 21
- The Maximum - 21 and minimum - 9, mark them with a small and short vertical
line.
• The numbers are already in order so the minimum and maximum numbers can be
easily read off as 9 and 21, and the middle number (median) can be read as 14. 9,
10, 10, 12, 13, 14, 17, 18, 19, 21, 21
As 14 is in the middle, draw a line on the box plot graph at number 14.
• Lower quartile: WILL ALWAYS BE BELOW THE MEDIAN. Hence, to find that
out, have to look at the lower half of the data (in range of 9-14). Again, Apply the
median method. (Start cancelling numbers before the middle median - 14). 9,10, 10,
12, 13, Therefore, the lower quartile (LQ) is 10.
