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Correlation Guessing Game
Look at the scatter plot. Guess the correlation coefficient (r) between -1 and +1.
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Background: Correlation and Regression
A scatterplot displays the form, direction, and strength of the relationship between two quantitative variables. Straight-line (linear) relationships are particularly important because a straight line is a simple pattern that is quite common. The correlation measures the direction and strength of the linear relationship. The least-squares regression line is the line that makes the sum of the squares of the vertical distances of the data points from the line as small as possible (these vertical distances, from each data point to the least-squares regression line, are called the residual values).
Use the first applet to experiment: add/remove points, compare the least-squares line to your own line, and notice how scatter affects the correlation.