Partial preview of the text
Download Entering and Plotting Data Points - Lecture Notes | MATH 124 and more Study notes Mathematics in PDF only on Docsity!
Csei0g and Plotting Data Points rie) First, you need to enter your data points in the list editor. To do this, select [STAT] You should see headings L1, L2, and L3. List the input values from your data points under Li, and the output values under L2. To display the data points that you just typed in, you need to tell the calculator thal you want to plot your data points instead of a standard function y = f(x). To do this, bit the |Y=| key just like you would if you were going to plot a function defined as a formula, and then activale Plot! at the top of your screen by placing the cursor over it and hitting [ENTER], Plot1 should now be highlighted, and when you hit [GRAPH], your data points will be plotted (along with any other functions or data that are active). A couple of notes. If you don’t see your data points when you hit [GRAPH], that probably means that the viewing window that you last selected doesn’t include your data points. You can have the calculator choose a viewing window for you that avonratically includes all data points by selecting [zoom] [9 [9:ZoomStat] and then hitting Also, your calculator will continue to display your data points every time you hit Tat you turn Plot off. To do this, just move the cursor to Plot1 and hit [ENTER,|so that Plotl is no longer highlighted. Finding a best-fit line (TI-83) When data appears approximately linear, it is useful to have an equation for the line that best fits the data. It is not always possible, of course, to find a line that goes through every single data point that we have; but if the data is approximately linear, we can still find a line that is “as close as possible” to all the data points as a group. For a given set of data, there are formulas which can be used to come up with this best-fit line by hand, but many scientific calculators have these formulas built in and will calculate the best-fit line for you after you enter the data. ‘ To find the best-fit line on your calculator, first enter the data points in L1 and L2 as described above under “Entering and Plotting Data Points.” At this point, there are two ways to ask your calculator to compute the best-fit line for you, both of which are listed below: (Note: LinReg stands for “Linear Regression” which is the name for. the process of finding a best-fit line for a set of data.) 1, [STAT] |CALC]| 4:LinReg(ax+b) |[ENTER 2. [STAT] | CALC ]} 4:LinReg(ax+b) || VARS |[Y-VARS]|1:Function || 1:Y; The first sequence will tell you what a and 6 are, so that the equation of your best-fit line will be = az +6, The second sequence goes a step farther and actually stores the best fit-line in the variable Y;. (If you hit Y= after executing the second sequence above, you'll see the equation of your best-fit line as computed by the calculator.) That means that if you hit GRAPH, the calculator will plot your data points together with the best-fit line. 
