Using your Ti‐83/84 to find the Best‐fit line By Richard Bankhead You have collected the following data in Table 1 and plotted it on the graph below in Figure 1. Table 1: Data Independent
Variable
(Units)
Dependent Variable
(Units)
1.2
2.1
3.5
4.0
5.5
6.0
2.3
4.0
6.8
9.0
10.4
13.1
Figure 1: Data plotted. You would like to determine the best‐fit equation for the line representing the relationship between the independent variable and the dependent variable in the form y = mx + b [1] The desired result is shown in Figure 2. 1 Best‐fiit Line Figure 2: D
Data Plotted w
with trend line and best‐fit linear equation
n. To use your Ti‐83/84 to
o solve this problem comp
plete the follo
owing steps.
1) P
Press the (STA
AT) key on your calculator and the following menu should appearr. 2) Press (1) to enter or edit daata. 2 Best‐fiit Line nter the Independent Variiable in the L1 Colum and tthe Dependen
nt Variable in
n the L2 Colum
mn. 3) En
4) Press the (STAT) key to exitt the editor 5) Press the (RIGH
HT ARROW) kkey to move tthe CALC men
nu. 6) Press (4) to acccess linear regression. 3 Best‐fit Line 7) At the prompt enter your data variables, L1 and L2 separated by a comma. To enter “L1” press [2nd][1] and to enter “L2” press [2nd][1] on your keypad. Press [ENTER]. 8) The following will be displayed representing the best‐fit line for your data. 9) To plot your best fit line press the [Y=] and enter your equation in “\Y1=”. 10) Turn on the STAT plot (data plot) for your data. Press [2nd] [Y=]. 4 Best‐fit Line 11) Press [1] to select “Plot1” 12) Use the arrow keys to move the cursor over “ON”. Press the [ENTER] key to change Plot1 from “OFF” to “ON”. Notice that the Xlist is set to L1 and the Ylist is set to L2. 13) Press the [WINDOW] key to set up the graph widow. Make the following changes and then press the [GRAPH] key to plot the data and best fit line. 14) You should see the following result. 5 Best‐fit Line 15) Be sure to turn off the STAT PLOT when you are finished. You can tell if you have a STAT PLOT turned on be pressing the [Y=] key. Notice that Plot1 is highlighted indicating that you have a STAT PLOT turned on. 16) You can clear data from a list such as L1 by pressing the [STAT] key and pressing [4] for “ClrList”. 17) At the prompt enter your data variables and clear both list at the same time. To enter “L1” press [2nd][1] and to enter “L2” press [2nd][1] on your keypad. Press [ENTER]. 6