STA201 Project 1 Tips. Generating Histograms with the TI-83Plus


This posting is primarily for students in my STA 201 Statistical Methods course, but it may be of interest to anyone using the TI-83Plus graphing calculator for statistical computations. Project 1 of my STA201 course involves obtaining numerical data (from sources given in class) and analyzing the first non-zero digit. In particular, we want to study the distribution of the first non-zero digit in the data sets.

Read More for a detailed description of how to use the TI-83Plus graphing calculator to obtain frequency distributions, relative frequency distributions, and histograms.


To use the TI-83Plus graphing calculator for statistical plots, you must first configure it for such plots. Press 2nd, Y= (STATPLOT). The default selections are shown in the following figure.




Select 1 in the figure above and set the options to look like the following figure.






Press 2nd, Mode (Quit) when you're done. If you press 2nd, Y= (STATPLOT) again, your screen should look like the one in the following figure.




Next, you should be ready to enter data. Since in the project, we're only interested in the first non-zero digit of each value, you should only enter that digit. For example, if your values are 134, 2300, 25, 234, 376, 991, 4567, 987, 654, and 76, then you should enter 1, 2, 2, 2, 3, 9, 4, 9, 6, and 7.

Press STAT to see a screen as the following one.



Next, press 1 for EDIT and enter the data under L1 as show below.



To see a histogram, press ZOOM followed by 9 (for ZoomStat)




This will show a histogram, but it may not be the one that you want.




Press TRACE and use the right and left arrow keys to see what bins have been selected and what the frequencies are for each bin.




Notice that the default gave us bins of width 2. We would like bins of width 1, centered at the digits 1, 2, 3, ..., 9. To achieve that you should press WINDOW to see the following screen.





Change the values to the ones shown in the following screenshot.






After setting the values as shown above, pressing GRAPH, followed by TRACE, produces the following screen.







Usie the arrow keys in the GRAPH window to determine the frequency for each digit, which is shown for each bin (i.e., for each digit 1,2 ,3 ..., 9) by the n-value at the bottom right of the screen. In the first of the preceding two figures, we see that the frequency of the digit 1 is 1, while the second of the two preceding figures shows that the frequency of the digit 9 is 2. In this process, you'll determine the largest frequency. You'll want to set the Ymax value in the WINDOW screen to a little larger than the maximum frequency. That way, the entire histogram will be shown in the screen when you subsequently press GRAPH.

To obtain the relative frequency, divide each frequency by the total number of values. In our example, we would divide each frequency by 10.

Keep in mind that the distribution that you'll obtain for the project will not look like the one developed here. The example shown in this posting was used only to demonstrate the process of obtaining the distribution.

See also, this tutorial for more information.


Posted: Thursday - November 09, 2006 at 06:59 AM        

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