SOLUTION Step 1: Getting your calculator ready Using your calculator, change the mode from normal to “Stat xy ”. Do this by pressing [2ndF] and then 2. This mode enables you to type in bivariate data. Step 2: Entering the data Key in the data row by row: Enter: 1 2 3 4 5
Press: (x, y) (x, y) (x, y) (x, y) (x, y)
Enter: 1 2,5 2,75 3,0 3,5
Press: DATA DATA DATA DATA DATA
See: n=1 n=2 n=3 n=4 n=5
Note: The [(x, y)] button is the same as the [STO] button and the [DATA] button is the same as the [M+] button. Step 3: Getting regression results from the calculator Ask for the values of the regression coefficients a and b. Press: RCL RCL
Press: a b
See: a = 0,9 b = 0,55
∴ yˆ = 0,9 + 0,55x
Worked example 8: Using the CASIO f x-82ZA PLUS calculator QUESTION Using a calculator determine the least squares line of best fit for the following data set. Learner Chemistry (%) Accounting (%)
1 52 48
2 55 64
3 86 95
4 71 79
5 45 50
For a Chemistry mark of 65%, what mark does the least squares line predict for Accounting? NB. If you have a SHARP calculator, ensure that you have done the previous worked example first. Once you have completed the previous worked example, attempt this example using your calculator and see if you get the same answer.
382
9.2. Curve fitting