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Scatter plots and trend lines worksheet

Grade 8 math, Common Core 8.SP.A.3. 6 problems with an answer key and worked steps. Free to print, and you can make new problems any time.

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Scatter plots and trend lines

Grade 8 math, Common Core 8.SP.A.3

Use each scatter plot or trend line to answer the questions.

  1. 1.
    Describe the association between shoe size and quiz score.
    012345678910024681012shoe sizequiz score
  2. 2.
    Which point doesn’t fit the pattern? Describe the association of the others.
    012345678910024681012hours of TV a daybooks read this month
  3. 3.
    Describe the association between hours of sunshine and tomatoes picked.
    012345678910024681012hours of sunshinetomatoes picked
  4. 4.
    Which point doesn’t fit the pattern? Describe the association of the others.
    012345678910024681012hours of practicefree throws made
  5. 5.
    The trend line for test scores (y) and hours studied (x) is y = 7x + 45. Predict the score for 3 hours of study.
  6. 6.
    The trend line y = 3x + 17 models the money saved in dollars after x weeks. What does the slope mean?
Free worksheets for grades 6 to 8 from StudyWiz, with answer keys: studywiz.online/worksheets

Answer key: Scatter plots and trend lines

Grade 8 math. Each answer has a few worked steps, to help check the method as well as the answer.

  1. 1. No association: the points don’t rise or fall together.

  2. 2. (6, 10). Negative linear association.

  3. 3. Positive linear association: as hours of sunshine goes up, tomatoes picked tends to go up.

  4. 4. (3, 11). Positive linear association.

  5. 5. 66

    y = 7(3) + 45 = 66

  6. 6. About $3 more is saved each week.

The answer key prints on its own page. You’re welcome to print and copy these worksheets for your own kids or class.

About scatter plots and trend lines

A scatter plot shows pairs of data as points, so you can see whether two things are related. If the points rise from left to right there is a positive association; if they fall, a negative one. A trend line is a straight line that fits the points closely, and its equation can be used to make predictions.

Worked example 1

The trend line for test scores (y) and hours studied (x) is y = 6x + 50. Predict the score for 6 hours of study.
  1. Step 1.y = 6(6) + 50 = 86

Answer: 86

Example 2

Describe the association between birth month and pets at home.
012345678910024681012birth monthpets at home

Answer: No association: the points don’t rise or fall together.

Watch out for

  • Positive association: as one goes up, the other tends to go up.
  • Use the trend line equation to predict: put in the x-value and work out y.
  • The slope of the trend line tells how much y changes, on average, for each 1 of x.

Practice scatter plots and trend lines online

On StudyWiz, your kid can practice scatter plots and trend lines with 5-question quizzes that are checked as they go, with an explanation for every answer. When a homework problem is the trouble, Wiz gives a hint for each step instead of the answer.

More grade 8 math worksheets

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See all 8th grade math worksheets, or switch to grade 6 or grade 7.

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