5-7 Scatter Plots and Trend Lines

Objectives

To write an equation of a trend line and of a line of best fit

To use a trend line and a line of best fit to make predictions

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In the Solve It, the number of albums downloaded per year and the number of CDs sold per year are related.

Essential Understanding You can determine whether two sets of numerical data are related by graphing them as ordered pairs. If the two sets of data are related, you may be able to use a line to estimate or predict values.

A scatter plot is a graph that relates two different sets of data by displaying them as ordered pairs. Most scatter plots are in the first quadrant of the coordinate plane because the data are usually positive numbers.

You can use scatter plots to find trends in data. The scatter plots below show the three types of relationships that two sets of data may have.

When y tends to increase as x increases, the two sets of data have a positive correlation.	When y tends to decrease as x increases, the two sets of data have a negative correlation.	When x and y are not related, the two sets of data have no correlation.

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