EXTENSION: Evaluating Associated Variables 1. Using the data in Table 1, construct and label a scatter plot using a computer program or hand-graphing that illustrates the association between beak depth and wing length for the birds that survived the drought of 1977. 2. Draw a trend line either by hand on your graphing paper or automatically by right-clicking on your data plot in Excel and choosing "add trendline." If you are doing this exercise in Excel, a window will pop up after you choose "add trendline." 3. Calculate the coefficient of determination, or r, using your calculator or spreadsheet program. This value represents the proportion of the variation in the y variable that is explained by the variation in the x variable. Values vary from 0 to 1; values near 0 mean there is little relationship between x and y. For example, if r is 0.90, the xvariable "explains" 90% of the variation in the y variable.