Constructing a Box Plot
A box plot (box-and-whisker plot) visually displays the five-number summary of a data set. To construct one: draw a number line covering the data range; draw a rectangle from Q1 to Q3; draw a vertical line at the median (Q2); extend whiskers from the box to the minimum and maximum values. For a data set with Min=10, Q1=15, Med=19, Q3=24, Max=30, the box spans from 15 to 24 with an inner line at 19. This skill from Reveal Math, Course 1, Module 10 is a core 6th grade statistical display.
Key Concepts
A box plot (or box and whisker plot) provides a visual image of the 5 Number Summary. To construct a box plot: 1. Draw a number line that covers the entire range of your data. 2. Draw a rectangle (the "box") that starts at Q1 and ends at Q3. This box represents the IQR (the middle 50%). 3. Draw a vertical line segment completely through the box at the Median (Q2). 4. Draw horizontal lines (the "whiskers") extending outward from the box to the Minimum and Maximum values.
Common Questions
How do I construct a box plot step by step?
Step 1: Draw a number line. Step 2: Mark Q1 and Q3, draw a rectangle between them. Step 3: Draw a vertical line at the median inside the box. Step 4: Draw whiskers from Q1 to the minimum and Q3 to the maximum.
What is the five-number summary?
The five-number summary consists of the minimum, Q1 (first quartile), median (Q2), Q3 (third quartile), and maximum. These five values are all you need to draw a box plot.
What does the box in a box plot represent?
The box represents the middle 50% of the data, from Q1 to Q3. Its width equals the Interquartile Range (IQR).
What do the whiskers in a box plot represent?
The whiskers extend from the edges of the box to the minimum value (left whisker) and maximum value (right whisker), showing the full range of the data excluding outliers.
Where does the median line go inside a box plot?
The median line is drawn vertically through the interior of the box at the Q2 value. It may not be centered in the box if the data is skewed.
When do 6th graders learn to construct box plots?
Module 10 of Reveal Math, Course 1 covers constructing box plots in the Statistical Measures and Displays unit.