Interpreting the correlation coefficient
• Fit a linear function for a scatter plot that suggests a linear association. • Use available technology to compute correlation coefficients. • Understand that the correlation coefficient measures the “tightness” of a line fitted to data. • Understand the significance of correlation coefficients close to 1 or –1. • Interpret the rate of change and constant term of a line fitted to data in the context of the data.
In this unit, students build on the statistical work they did in grade 8. Using technology, they represent data on two variables on a scatter plot, find the line of best fit, and interpret the slope and intercepts in context. They assess the fit of a line to data more precisely by plotting and analyzing residuals. Students compare strength of associations between different pairs of variables by interpreting correlation coefficients which they compute using technology. They gain experience in distinguishing between correlation and causality. Modeling is an intrinsic part of the high school statistics and probability standards and of this unit.