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9th grade · Math · Unit 9 of 22

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.

New York State Learning Standards learning standard: AI-S.ID.1; AI-S.ID.6; AI-S.ID.7 · box plots, scatter plots and the slope and intercept of a line 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 New York

In the New York State Learning Standards, this is unit 9 of 22 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: New York State Education Department (NYSED)

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: 38, 44, 28, 42, 36, 30, 46, 32. What is the median?

    answer box

  2. Question 2

    In a box plot, what does the box show?

    • Only the median
    • All of the data from least to greatest
    • The lowest 25% of the data
    • The middle 50% of the data, from Q1 to Q3

  3. Question 3

    Eight students recorded the minutes they read last night: 39, 35, 25, 47, 45, 51, 37, 29. What is the first quartile, Q1?

    answer box

  4. Question 4

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

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

  5. Question 5

    Eight students recorded the minutes they read last night: 24, 20, 32, 30, 12, 18, 38, 14. What is the interquartile range (Q3 − Q1)?

    answer box

  6. Question 6

    On a box plot, the median line is much closer to Q1 than to Q3. What does this tell you?

    • The mean must equal the median
    • The data between the median and Q3 is more spread out than the data between Q1 and the median
    • There are no values below the median
    • The data between Q1 and the median is more spread out

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