Lesson 12


  • Let's understand variability in situations.

12.1: Estimation: Average Book Length

Image of 3 books. Left book is longest, middle book is 276 pages, right book is shortest.

The book in the center is 276 pages long. What is the mean number of pages of the 3 books?

  1. Record an estimate that is:
     too low  about right   too high 
  2. Explain your reasoning.

12.2: The Better Option

Choose the best option based on the given data. Use a measure of center and measure of variability to justify your answers.

Participants’ ages at camp A

Dot plot from 10 to 14 by 1’s. Age of participants. Number of dots above each increment starting at 10 is 4, 5, 5, 0, 0.

Participants’ ages at camp B

mean: 11.93 years, mean absolute deviation: 1.65 years

Servers’ tip amounts at restaurant A

mean: $15, mean absolute deviation: $1.5

Servers’ tip amounts at restaurant B

Dot plot from 6 to 26 by 1’s. Tip amounts in dollars. 7.5, 1 dot. 10, 2 dots. 13, 1 dot. 14, 3 dots. 15, 2 dots. 16, 1 dot. 18, 2 dots, 20, 1 dot. 25, 1 dot. All other increments have 0 dots.
  1. ​​​​​​Which camp would you prefer to work for? Explain your reasoning.
  2. Which camp would you prefer to attend? Explain your reasoning.
  3. At which restaurant would you want to be a server? Explain your reasoning.

12.3: Notice and Wonder: Preschool Heights

Mai and Tyler both visit the same preschool classroom and measure the heights of people in the room in inches. The summary of their results are shown in the box plot and statistics.

What do you notice? What do you wonder?

Mai's results

Box plot from 30 to 70 by 5’s. Height in inches. Whisker from 30 to 31. Box from 31 to 39 with vertical line at 35. Whisker from 39 to 41.

mean: 35.2 inches, mean absolute deviation: 3.24 inches

Tyler's results

Box plot from 30 to 70 by 5’s. Height in inches. Whisker from 30 to 32 point 5. Box from 32 point 5 to 40 with vertical line at 35 point 5. Whisker from 40 to 70.

mean: 39.3 inches, mean absolute deviation: 7.19 inches