# TI-82: Histograms, BoxPlots

You can use the calculator to draw histograms, box-plots, and compute the frequency of each class.

See the instructions on using the calculator to do statistics and lists. This provides an overview as well as some helpful advice for working with statistics on the calculator.

## Histograms

1. Enter the data.
2. Determine the class width and the lower class boundary (not limit) of the first class using the techniques for creating grouped frequency distributions.
3. Turn off any regular plots: Hit Y= and position the cursor over any equal sign which is in inversed video (white on black) by arrowing left and then down if necessary. Hit enter while the cursor is on the equal sign to toggle between displaying the function (equal sign highlighted) and not displaying the function (equal sign not highlighted).
4. Press the STATPLOT key (2nd Y=)
5. Select a plot (usually plot 1) and hit enter
6. Turn the plot on by highlighting the ON and pressing enter.
7. Set the TYPE to histograph (last type)
8. Set the XLIST to the list you put the data into
9. Set the FREQ to 1.
10. Select WINDOW
11. Put the lower class boundary for the first class in XMIN
12. The XMAX value should be the lower class boundary for the first class plus the number of classes times the class width.
13. The Class Width should be stored in XSCL
14. YMIN should be set to 0
15. YMAX should be at least the largest frequency in any class. This is difficult to know if you're generating the histogram without first writing the table by hand. If the histogram displayed doesn't fit on the screen, go back and change this number. A good initial guess might be the sample size divided by the number or classes. You might round up it to a nice number (multiple of 5) or add one or two so that graph is completely shown on the screen.
16. YSCL should be set based on the YMAX value. A factor of YMAX would be a good choice (so if YMAX is 30, let YSCL be 5). If your YMAX is small (say under 10), you might want to set it to 1. This will determine how many marks are placed along the vertical axis.
17. Hit the GRAPH key.

## Finding the Frequency

1. Generate a histogram first
2. Hit the TRACE key
3. The "min" value is the lower class boundary
4. The "max" value is the upper class boundary
5. The "n" value is the frequency for that class.
6. Use the left and right arrow keys to get the values for all the classes.

## Box Plots

1. Enter the data.
2. Turn off any regular plots: Hit Y= and position the cursor over any equal sign which is in inversed video (white on black) by arrowing left and then down if necessary. Hit enter while the cursor is on the equal sign to toggle between displaying the function (equal sign highlighted) and not displaying the function (equal sign not highlighted).
3. Press the STATPLOT key (2nd Y=)
4. Select a plot (usually plot 1) and hit enter
5. Turn the plot on by highlighting the ON and pressing enter.
6. Set the TYPE to box-plot (3rd type)
7. Set the XLIST to the list you put the data into
8. Set the FREQ to 1.
9. Zoom to Statistics mode (ZOOM 9)

You hit the TRACE key with the box plot displayed to find the five numbers associated with it. You may use the left and right arrow keys to find all five numbers. Note that the calculator uses the quartiles instead of the hinges. The hinges and quartiles are the same unless the remainder when the sample size is divided by four is three.