485 APPLET Correlation by Eye 9.1 ACTIVITY You can find the interactive applet for this activity at MyLab Statistics. SECTION 9.1 Correlation 485 The Correlation by eye applet allows you to guess the sample correlation coefficient r for a data set. When the applet loads, a data set consisting of 20 points is displayed. To add a point, click at the desired location or click Add point and enter the coordinates. To remove a point, click and drag the point outside the axis area. You can change the Sample size by entering a new value. Click Simulate to generate a new set of points. Click Reset to remove all the points. Enter a Guess for r and click Check to see if you are within 0.1. Click Show to see the value of r. EXPLORE Step 1 Add five points to the plot. Step 2 Enter a Guess for r. Click Check. Step 3 Click Show. Step 4 Enter a new Sample size and click Simulate. Step 5 Remove five points from the plot. Step 6 Repeatedly enter a Guess for r and Check its value until you are within 0.1. Then Show the value of r. DRAW CONCLUSIONS 1. Generate a new data set. Using your knowledge of correlation, try to guess the value of r for the data set. Repeat this 10 times. How many times were you correct? Describe how you chose each r value. 2. Describe how to create a data set with a value of r that is approximately 1. 3. Describe how to create a data set with a value of r that is approximately 0. 4. Try to create a data set with a value of r that is approximately -0.9. Then try to create a data set with a value of r that is approximately 0.9. What did you do differently to create the two data sets? APPLET Guess: Correlation: Correlation by eye Try to guess the sample correlation within +/– 0.1 0 5 x 10 15 0 5 10 15 y Simulate Sample size Add point Reset Info 20 Check Show
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