Key takeaway: This grade 8 scatter plots test holds eight tasks, one of which has you build a plot, for 20 marks. The standard tested is 8.SP.A.1 for 8th grade, and the scoring key lives on its own page.
Describe patterns with the variable names, because vague answers lose points.
This test covers standard 8.SP.A.1 with 8 questions worth 20 points. Students read and construct scatter plots, describe association, and identify clusters and outliers. Complete answers use words such as positive, negative, linear, nonlinear, cluster and outlier. Use a ruler for the graph.
- Grade: Grade 8
- Chapter: Scatter Plots and Association
- Common Core: 8.SP.A.1
- Time: 45 minutes
- Total: 20 points (Question 1: 2 pts; Question 2: 2 pts; Question 3: 2 pts; Question 4: 3 pts; Question 5: 4 pts; Question 6: 3 pts; Question 7: 2 pts; Question 8: 2 pts)
Grade 8 Scatter Plots Test: questions 1–5
1. Read points on a scatter plot (2 points)
The scatter plot shows temperature and cups of cocoa sold.
- Write the coordinates of point A. (1 point)
- Explain what point B means in this situation. (1 point)
2. Describe the association (2 points)
Describe the association between the variables in the scatter plot. Give the direction and tell whether it is linear or nonlinear.
3. Linear or nonlinear (2 points)
The scatter plot shows the value of a car at different ages. Is the association linear or nonlinear? Support your answer.
4. Clusters and outliers (3 points)
The scatter plot shows weight and gas mileage for nine vehicles.
- Identify the outlier and give its coordinates. (1 point)
- Describe the clusters. (1 point)
- Describe the overall association. (1 point)
5. Construct a scatter plot (4 points)
The table shows daily screen time and nightly sleep for eight students.
| Screen time (hours) | Sleep (hours) |
|---|---|
| 1 | 9 |
| 2 | 9 |
| 3 | 8 |
| 4 | 8 |
| 5 | 7 |
| 6 | 6 |
| 7 | 6 |
| 8 | 5 |
- Plot the eight points on the grid. (2 points)
- Describe the association. (1 point)
- Explain what it means for these students. (1 point)
Grade 8 Scatter Plots Test: questions 6–8
6. Classify the association (3 points)
Tell whether a scatter plot of each pair would show a positive association, a negative association, or no association.
- A person’s height and arm span (1 point)
- The outside temperature and a family’s heating bill (1 point)
- A student’s shoe size and the number of siblings (1 point)
7. Association and cause (2 points)
A scatter plot shows a positive association between the number of firefighters at a fire and the damage the fire causes. Does that mean sending more firefighters causes more damage? Explain.
8. Evaluate a claim about an outlier (2 points)
Sofia looked at the scatter plot and said, “There is no outlier, because every point is inside the axes.” Is she correct? Explain.
What does the grade 8 scatter plots test include?
Question 1 reads point A on the cocoa plot. Then question 2 asks for the direction and the strength of an association. Question 3 asks whether the car-value pattern is linear, and you must support your choice.
Question 5 is the longest, worth 4 points. You plot eight students’ screen time against sleep, so scale the axes first.
What should you rehearse before the scatter plot test?
Start by naming association from a quick sketch. Next, rehearse the vocabulary of cluster and outlier. Finally, plot one small table with a ruler.
- Question 4 asks for an outlier and its coordinates.
- Question 6 classifies three variable pairs.
- Question 8 checks Sofia’s claim that no outlier exists inside the axes.
How do you handle the cause question?
Question 7 pairs firefighters with fire damage. Say that bigger fires need more firefighters and cause more damage, so the number of firefighters is not the cause. Because the key rewards that reasoning, include it.
What is the right follow-up to this scatter plot test?
Mark your paper with the key, then redo any plot you drew poorly. Next, rewrite question 8 as a complete argument. If the construction question cost points, rehearse choosing a scale that fits every value.
See every chapter on the Grade 8 math page.
