Now you must find the median of the upper and lower halves of the data, remember these median are called the upper and lower quartile. Draw a number line starting with the minimum and ending with the maximum. Then plot the median, upper quartile, and the lower quartile on the number line. Finally, draw a box around the upper and lower quartile points and divide the box in two parts at the median. The portion of the number line that is not in side the box is sometimes called the whiskers.
Outliers are the points in the data set that lie out side the box and whisker plot.
The math term that is used for the data inside the box is the inner quartile range. The inner quartile range is calculated by subtracting the lower quartile from the upper quartile. To calculate the extreme range you must use the inner quartile range. To calculate the lower end you must multiply the inner quartile range by the number written beside the extreme range in the applet then subtract that number from the lower quartile. To find the upper end you must take that same number and add it to the upper quartile.