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8th grade · Math · Unit 5 of 11

Scatter Plots & Stories

Two-variable data and misleading graphs

What your child practices

Deciding when two-variable data is needed, picking the best graph, describing scatter plots as strong, weak, positive, negative or none, spotting outliers, and noticing graphs that mislead.

Minnesota K-12 Academic Standards benchmark: 8.1.1.2; 8.1.1.3 · scatter plots and lines that model a pattern

How we explain it

Children can open this short lesson before they practice.

  1. A scatter plot shows two sets of data as points.
  2. Points that rise together show a positive relationship.
  3. A point far from the pattern is an outlier.

Example: As study time goes up, test scores go up. What kind of relationship is that? Both values rise together. That is a positive relationship. Answer: Positive

Scatter Plots & Stories in Minnesota

In the Minnesota K-12 Academic Standards, this is unit 5 of 11 in 8th grade Math, after Big, Small & Real Numbers and before Tables, Graphs & Linear Relations.

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

    All of the points but one lie on a line. Which point is the outlier?

    Points on a scatter plot
    xy
    13
    25
    37
    4-10
    511
    613
    • (3, 7)
    • (2, 5)
    • (4, −10)
    • (1, 3)

  2. Question 2

    Which graph is best for showing what part of a monthly budget goes to each category?

    • a circle graph
    • a line graph
    • a histogram
    • a scatter plot

  3. Question 3

    Which question needs two-variable data?

    • How does a plant's height change with the hours of sunlight it gets?
    • What color is each car in the parking lot?
    • How many students ride the bus each day?

  4. Question 4

    Which variable is continuous?

    • the number of apples in a bag
    • the number of seeds in an apple
    • the number of trees in an orchard
    • the mass of an apple

  5. Question 5

    A line graph uses a very stretched vertical scale. What can this do?

    • Make the data more accurate.
    • Turn the data into a circle graph.
    • Make a small change look dramatic.
    • Hide every change in the data.

  6. Question 6

    Which best describes the relationship between the number of hours spent reading and the length of a person's arm?

    • a positive relationship
    • no relationship
    • a negative relationship

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