Instructions

• Vary r interface: This interface has two options
  • Set r: with this option, the user specifis a value of the correlation coefficient, r and the SDs for the independent (x) and dependent (y) variables. The applet randomly a plot that matches those criteria. Each time the 'New Plot' button is clicked, the applet generates a new plot that again matches the selected criteria.
  • Animate: Beginning with a plot for which r=1, the applet displays a sequence of plots for which the correlation coefficient of each is less than that of the preceding plot by a user specified increment. r = -1 for the final plot in the sequence. The user can adjust the animation speed and can adjust the SDs of the variables.
• Compare Plots interface: The applet displays 2 or 4 plots simultaneously. For each plot, the user can adjust the value of r and the SDs of the variables facilitating comparisons among plots.
• Guess r interface: The applet displays a randomly generated plot and the user estimates the value of r. After the guess is made, the applet displays the true value of the correlation coefficient. The correlation between the user's guesses and the true values of r is displayed as the 'scorr'.
• Guess Plot interface: The applet displays four plots and asks for which plot correlation coefficient is a specified value. The user's task is to choose the plot with the given correlation. After the choice is made, the applet displays the the correct answer. The applet also displays the number of correct responses and the 'scorr'. There are three levels of difficulty available for this interface.
• Order Plots interface: The applet displays four plots. Next to each plot are 5 to 6 (depending on level) radio buttons each labeled with a value of r. The user's task is to select the radio button attached to the correct value of the correlation coefficient for each plot. After the user submits responses, the applet displays the the correct answers. Correct responses are displayed in green. If a user chooses a response that is not the correct one, the user's response is shown in red. If the user presses submit without having selected a value of r for one or more plots, the value of the correlation coefficient for that plot is shown in orange. The applet also displays the percent of correct responses and the 'scorr'. There are three levels of difficulty available for this interface.