Subscribe

9th grade · Math · Unit 13 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.

Alabama Course of Study content standard: GDA.9; GDA.12; GDA.13 · box plots and scatter plots, lines of fit 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

Data & Scatter Plots in Alabama

In the Alabama Course of Study, this is unit 13 of 18 in 9th grade Math, after Volume & Units and before Statistics in Society.

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: Alabama State Department of Education (ALSDE)

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

    As the number of hours of study goes up, test marks tend to go up too. What kind of correlation is this?

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

  2. Question 2

    Eight students recorded the minutes they read last night: 60, 56, 52, 40, 46, 34, 50, 58. What is the interquartile range (Q3 − Q1)?

    answer box

  3. Question 3

    Ice cream sales and sunburn cases both rise in July. What is the best explanation?

    • Hot weather affects both, so one does not cause the other
    • Ice cream causes sunburn
    • The data must be wrong
    • Sunburn makes people buy ice cream

  4. Question 4

    A line of best fit for hours of practice (x) and score (y) is y = 2x + 27. What score does the model predict after 5 hours?

    answer box

  5. Question 5

    Eight students recorded the minutes they read last night: 19, 29, 17, 27, 21, 37, 31, 15. What is the first quartile, Q1?

    answer box

  6. Question 6

    Eight students recorded the minutes they read last night: 40, 26, 20, 48, 42, 36, 32, 30. What is the median?

    answer box

More 9th grade