# TI-82: Plotting an Ogive

The Ogive is a frequency polygon (line plot) graph of the cumulative frequency
or the relative cumulative frequency.

The horizontal axis is marked with the class boundaries and the vertical axis
is the frequency. All class boundaries are used -- there will be one more class
boundary than the number of classes.

The following example assumes the class boundaries are in List 1 and the cumulative
frequencies are in List 2. You are free to use any two lists that you desire,
but you should make the appropriate adjustments in the instructions if you
don't use List 1 and List 2.

- Enter the class boundaries into List 1. Start with the lower boundary of
the first class and end with the upper boundary of the last class.
- Enter the cumulative frequencies into List 2. Start with 0 for the first
value because there is nothing less than the first lower class boundary.
- 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).
- Press the STATPLOT key (2nd Y=)
- Select a plot (usually plot 1) and hit enter
- Turn the plot on by highlighting the ON and pressing enter.
- Set the TYPE to LinePlot (2nd type)
- Set the XLIST to List 1
- Set the YLIST to List 2
- Set the MARKER to any of the three values
- Select WINDOW
- Put the lower class boundary for the first class in XMIN
- The XMAX value should be the upper class boundary of the last class
- The Class Width should be stored in XSCL
- YMIN should be set to 0
- YMAX should be set to the total frequency if using cumulative frequencies
in List 2 and set to 1.00 if using relative cumulative frequencies in List
2.
- YSCL should be set appropriately based on YMAX.
- Hit the GRAPH key.

### Relative Frequencies

There is no need to re-enter the data if you wish to use relative cumulative
frequencies instead of cumulative frequencies.

The following assumes that the cumulative frequencies are in List 2.

*Replace the ### by the total frequency. You can't put "###" into
the calculator*.

L2 / ### STORE L2

This will replace the cumulative frequencies with the relative cumulative
frequencies.

To replace relative cumulative frequencies with cumulative frequencies, change
the division to multiplication.

L2 * ### STORE L2