Step 3: Explore the data - Numbers
Visual impressions of the strength of the relationship revealed by a scatterplot can be heavily influenced by scaling, etc. A numerical summary of the strength of the linear relationhip is r, the correlation coefficient. Press Begin to view the demo below. Read the blue text boxes as they appear and then watch how the scatterplot changes to match different values of the correlation coefficient. Once the demo is finished, scroll down for further instructions. [Press the arrow to view the demo again.]
Toggle back (e.g., alt-tab) to the Correlation/Regression applet, check the box next to Correlation coefficient to compute the correlation coefficient (r).
(c) Provide the value of this correlation coefficient in your lab report. Does the correlation coefficient indicate a positive or a negative linear association for these data? Does it seem strong (r close to 1 or -1) or weak (r close to zero)?
