While there are plenty of methods to get a good hand drawn graph of a linear equation, many plot more points than necessary and (if you aren’t careful) misrepresent the location of two important points: the x and y intercepts.
Using the intercepts to plot your line takes care of both of these problems and more importantly: its fast! In this video, I will use two examples to show you exactly how it’s done.
http://www.mathbootcamps.com/media/fastgraphsoflinearequations.mp4In the past week or so, we have covered how to read a histogram and how to sketch a histogram by hand. Today I’m going to show you how to get a histogram on your TI83 or 84 calculator. Using this, you can get a quick look at the patterns in any data set and let the calculator do the work for you when you need to turn in a hand drawn graph.
Don’t worry if you still need some help after the video! I also have made a one page handout that you can download right here: (just right click and select save as) Histograms on the Calculator Cheat Sheet (PDF) and if you scroll a little bit, you will find a little more explanation about each of the steps I do in the video.
| 12 14 14 14 16 |
18 20 20 21 23 |
27 27 27 29 31 |
31 32 32 34 36 |
40 40 40 40 40 |
42 51 56 60 65 |
To get to the lists in your calculator, press STAT and then choose 1:EDIT. There are several lists to choose from but L1 is the default list on the other menus. This means that if you use L1, you will have less stuff to change in the calculator later.
To enter data, type the number and then press ENTER. Again, it is really important that all of the data goes into one list – even if in your book it is in different columns.
Once the data is entered, press 2ND and then Y= to get in the statplot menu. Under this menu, go into plot 1 (you can use any plot, but again, this is the easiest to work with) and turn the plot on. Once the plot is on, select the histogram by highlighting it and pressing enter, and make sure the list says L1. If you used a different list, you will have to change the list here. Finally, leave “frequency” as 1.
Once your plot is on, press ZOOM and then #9 ZOOMSTAT to see your graph. The TRACE button allows you to see what the groups/classes are and the frequency. Often, the class width the calculator uses isn’t very natural. In this example its 8.8. It’s a good idea to change this to something that is easier to work with and in this example I decided to change this to 9.
To do this, you press WINDOW and adjust the number next to XSCL. Once you do this, press GRAPH to see your changes since pressing ZOOMSTAT will make the calculator recalculate everything.
In the last image, “n” is the frequency of the class denoted by the two numbers in the inequality. For example, the highlighted class in the last picture goes from 12 to 21 and has a frequency of 8.
What if there is an error?
If you get all the way to the end and then your graph won’t show up, I would make sure there is nothing under “Y=”. Sometimes when you walk around, your calculator accidently gets turned on and a bunch of stuff can get pressed and typed under Y=. If this doesn’t fix it, I would then make sure everything is under L1 and not some other list. You can reset your list by clicking STAT, EDIT, SETUPEDITOR if you have a weird menu.