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9th grade · Math · Unit 9 of 17

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.

Minnesota K-12 Academic Standards benchmark: 9.1.1.10; 9.1.1.11 · scatter plots, box plots and lines of best fit

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

Data & Scatter Plots in Minnesota

In the Minnesota K-12 Academic Standards, this is unit 9 of 17 in 9th grade Math, after Lines & Intersections and before Function Notation.

Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.

Source: Minnesota Department of Education (MDE)

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: 40, 38, 46, 56, 62, 32, 50, 54. What is the median?

    answer box

  2. Question 2

    Eight students recorded the minutes they read last night: 63, 47, 57, 41, 33, 45, 39, 53. What is the interquartile range (Q3 − Q1)?

    answer box

  3. Question 3

    A line of best fit for hours of practice (x) and score (y) is y = 3x + 5. What score does the model predict after 4 hours?

    answer box

  4. Question 4

    A correlation coefficient is r = −0.92. What does it tell you?

    • No correlation
    • A strong positive correlation
    • A strong negative correlation
    • A weak negative correlation

  5. Question 5

    As the outdoor temperature falls in winter, the heating bill tends to rise. What kind of correlation is this?

    • A perfect correlation
    • Positive correlation
    • No correlation
    • Negative correlation

  6. Question 6

    A fitness app stores a user's location every minute for years. Which is a possible consequence?

    • It uses no storage space
    • Nobody can learn anything from it
    • Private information could be misused if it is shared without permission
    • The data can never be wrong

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