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9th grade · Math · Unit 9 of 18

Data & Scatter Plots

Quartiles, box plots and correlation

What your child practices

Finding the median and quartiles of a data set, reading a box plot, telling positive, negative and no correlation apart, and using a line of best fit to make predictions. Correlation does not prove one thing causes another.

California Content Standards learning standard: S-ID.1; S-ID.6; S-ID.7 · box plots, scatter plots and the strength of an association

How we explain it

Children can open this short lesson before they practice.

  1. A box plot shows the minimum, Q1, median, Q3 and maximum.
  2. A scatter plot shows how two variables relate.
  3. A line of best fit follows the trend.

Example: Data: 2, 4, 6, 8, 10. What is the median? Data is already in order. The middle value is 6. Answer: 6

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    Eight students recorded the minutes they read last night: 23, 17, 29, 11, 27, 39, 15, 35. What is the median?

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  2. Question 2

    A line of best fit for hours of practice (x) and score (y) is y = 3x + 8. What score does the model predict after 4 hours?

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  3. Question 3

    A line of best fit is used to…

    • Join every point exactly
    • Make the data larger
    • Prove one variable causes the other
    • Describe the trend and predict values

  4. Question 4

    Shoe size and test marks for a class are plotted. The points look scattered with no pattern. What does that suggest?

    • A strong positive correlation
    • There is little or no correlation
    • A strong negative correlation
    • The data must be wrong

  5. Question 5

    Eight students recorded the minutes they read last night: 50, 48, 42, 32, 56, 36, 46, 38. What is the first quartile, Q1?

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  6. Question 6

    Eight students recorded the minutes they read last night: 49, 43, 53, 33, 41, 37, 59, 27. What is the interquartile range (Q3 − Q1)?

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