Math 8 Lesson: Box Plots
Here are the birth weights, in ounces, of all the puppies born at a kennel in the past month.
13 14 15 15 16 16 16 16 17 17 17 17 17 17 17 18 18 18 18 18 18 18 18 19 20 What do you notice and wonder about the distribution of the puppy weights?
Twenty people participated in a study about blinking. The number of times each person blinked while watching a video for one minute was recorded. The data values are shown here, in order from smallest to largest.
3 6 8 11 11 13 14 14 14 14 16 18 20 20 20 22 24 32 36 51
Use the grid and axis to make a boxplot of this data set.
Find the median (Q2) and mark its location.
Find the first quartile (Q1) and the third quartile (Q3). Mark their locations.
A box plot can be used to represent the five-number summary graphically. Let’s draw a box plot for the number-of-blinks data.
- Draw a box that extends from the first quartile (Q1) to the third quartile (Q3). Label the quartiles.
- At the median (Q2), draw a vertical line from the top of the box to the bottom of the box. Label the median.
- From the left side of the box (Q1), draw a horizontal line (a whisker) that extends to the minimum of the data set. On the right side of the box (Q3), draw a similar line that extends to the maximum of the data set.
What are the minimum and maximum values?
You have now created a box plot to represent the number of blinks data. What percentage of the data values are represented by each of these elements of the box plot?
The left whisker
The box
The right whisker
Suppose there were some errors in the data set: the smallest value should have been 6 instead of 3, and the largest value should have been 41 instead of 51. Determine if any part of the five-number summary would change. If you think so, describe how it would change. If not, explain how you know.