8th grade · Math · Unit 11 of 17
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.
Washington State Learning Standards learning standard: M.8.DA.SP.1; M.8.DA.SP.2 · scatter plots and patterns of association
How we explain it
Children can open this short lesson before they practice.
- A scatter plot shows two sets of data as points.
- Points that rise together show a positive relationship.
- 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
Sample questions
A taste of this unit. In the app, questions change every time and get easier or harder to match your child.
Question 1
On a scatter plot, as the x-values increase, the y-values go down. The points are loosely scattered around a line. How would you describe the relationship?
- strong negative
- weak negative
- weak positive
- strong positive
weak negative
Hint: Positive means both go up together; negative means one goes up as the other goes down. Strong means the points are close to a line.
Question 2
A student collects data on hours of practice and number of free throws made. Which graph best shows whether the two are related?
- a pictograph
- a bar graph with one bar
- a scatter plot
- a circle graph
a scatter plot
Hint: Two numerical variables measured for each person fit a scatter plot.
Question 3
The points on a scatter plot are spread out with no pattern. How would you describe the relationship?
- strong positive
- none
- strong negative
- weak positive
none
Hint: If one variable does not predict the other, there is no relationship.
Question 4
All of the points but one lie on a line. Which point is the outlier?
Points on a scatter plot x y 1 10 2 14 3 18 4 35 5 26 6 30 - (4, 35)
- (2, 14)
- (1, 10)
- (3, 18)
(4, 35)
Hint: An outlier does not fit the pattern of the other points. Find the point that is far from the line the others make.
Question 5
Every graph should show…
- the largest values at the left
- a title, labeled axes, a suitable scale and a source
- only the data points
- the most colorful design
a title, labeled axes, a suitable scale and a source
Hint: These features let readers understand and trust the graph.
Question 6
A graph has no title and no labels on its axes. What is the problem?
- Nothing, because the shape tells the story.
- Readers cannot tell what the data shows.
- The data must be wrong.
- The graph must be a scatter plot.
Readers cannot tell what the data shows.
Hint: A good graph has a title, labels, units and a source.