Lesson 7

Observing More Patterns in Scatter Plots

Let's look for other patterns in data.

7.1: Notice and Wonder: Nonlinear Scatter Plot

What do you notice? What do you wonder?

A scatterplot.


 

7.2: Scatter Plot City

Your teacher will give you a set of cards. Each card shows a scatter plot.

  1. Sort the cards into categories and describe each category.
  2. Explain the reasoning behind your categories to your partner. Listen to your partner’s reasoning for their categories.
  3. Sort the cards into two categories: positive associations and negative associations. Compare your sorting with your partner’s and discuss any disagreements.
  4. Sort the cards into two categories: linear associations and non-linear associations. Compare your sorting with your partner’s and discuss any disagreements.

7.3: Clustering

How are these scatter plots alike? How are they different?

Four scatterplots.

 

Summary

Sometimes a scatter plot shows an association that is not linear:

Scatterplot, x, 0 to 12 by 3, y, 0 to 30 by 6. Points begin near 1 comma 24 and trend down and to the right until about 6 comma 2, and then trend up and to the right to about 11 comma 25.

We call such an association a non-linear association. In later grades, you will study functions that can be models for non-linear associations.

Sometimes in a scatter plot we can see separate groups of points.

A scatterplot with two groups of points.  

We call these groups clusters. 

Glossary Entries

  • negative association

    A negative association is a relationship between two quantities where one tends to decrease as the other increases. In a scatter plot, the data points tend to cluster around a line with negative slope.

    Different stores across the country sell a book for different prices.

    The scatter plot shows that there is a negative association between the the price of the book in dollars and the number of books sold at that price.

    Scatterplot with line of best fit.
  • outlier

    An outlier is a data value that is far from the other values in the data set.

    Here is a scatter plot that shows lengths and widths of 20 different left feet. The foot whose length is 24.5 cm and width is 7.8 cm is an outlier.

    A scatterplot with line.
  • positive association

    A positive association is a relationship between two quantities where one tends to increase as the other increases. In a scatter plot, the data points tend to cluster around a line with positive slope.

    The relationship between height and weight for 25 dogs is shown in the scatter plot. There is a positive association between dog height and dog weight.

    A scatterplot, horizontal, dog height in inches, 6 to 30 by 3, vertical, 0 to 112 by 16. Same scatterplot as previous, this time with a line through 9 comma 0 and 27 comma 80.