Scatter Plots and Associations

​Scatter Plots and Association

B.E.S.T. Standards

8.DP.1.1 – Given a set of real-world, bivariate numerical data, construct a scatter plot of a line graph as appropriate for the context.

8.DP.1.2 – Given a scatter plot within a real-world context, describe patterns of association.

8.DP.1.3 – Given a scatter plot within a linear association, informally fit a straight line.

8.AR.3.5 – Given a real-world context, determine and interpret the slope and the 𝑦𝑦- intercept of a two-variable, linear equation from a written description, a table, a graph, or an equation in slope-intercept form.

Essential Questions

• How can you construct and interpret a scatter plot?

• How can you describe the data set on a plot?

• Scatter plots are graphs that use points to display numerical data with two variables, or bivariate data

• Scatterplots can help determine if one variable has an effect on the other, or if there are overall trends, patterns, or associations between the variables.

Scatter Plots

Fill in the Blank

Zara surveyed shoppers at a mall to see how many items they’d purchased and the total amount of money they’d spent at the mall. She used the data to create the scatter plot shown.

How many shoppers did Zara survey?

Fill in the Blank

Zara surveyed shoppers at a mall to see how many items they’d purchased and the total amount of money they’d spent at the mall. She used the data to create the scatter plot shown.

Does the number of items purchased seem to have an effect on the amount of money a shopper spent?

As one variable increases, the other variable increases.

(The variables change in the same direction.)

Positive Association

As one variable increases, the other variable decreases.

(The variables change in the opposite direction.)

Negative Association

The change in one variable has no effect on the second variable.

No Association

Match

Match the type of association you'd expect to see between the following variables

• The number of shoes a person owns and the number of states they've visited

• The size in ounces of a steak and the cost of the steak

• The number of days since watering a plant an the moisture level of the soil

no association

positive

negative

• no association

• positive

• negative

Strength of Association

If data points are close together, the association is strong , and if the data points are widely spread the association is weak .

Linear vs Non-linear

If a straight line can be drawn to show the overall trend of a scatterplot, the association can be described as linear .

Multiple Select

Which graph(s) show linear association

Multiple Select

Which graph(s) show non-linear association

Multiple Choice

Which scatterplot shows the weakest association?

Multiple Choice

Which scatterplot shows the strongest association?

Draw

Draw a line from each scatterplot to the best description of its association and then to the variables is would most likely represent. Not all choices will be used.

Essential Questions

• How can you construct and interpret a scatter plot?

• How can you describe the data set on a plot?