Histograms & Boxplots

This page will cover some very basic TI-83 options.

Please note: This is not a "how-to" guide for your calculator. You already have one of those - the manual! You are advised to keep the manual for your calculator handy at all times. You will need to reference it often. Go to www.ti.com/calc/docs/guides.htm if you have misplaced your manual.

The easiest way to enter a list of data is to use STAT Edit. Suppose we wish to enter the following list:

25, 18, 12, 27, 34, 48

Let us enter it into the default list L_{1}.

Leave the editor by pressing <2^{nd}>QUIT.

Note: If you need to clear old data from a list, one way is the following:

Move the cursor up to highlight the list name, press ENTER, CLEAR, then ENTER again.

You can clear the data from all of the lists by doing this:

Press <2^{nd}>MEM,
ClrAllLists, then ENTER.

If your STAT Editor does not show lists
L_{1} - L_{6},
you can reset to the default like so:

Press STAT, SetUpEditor, then ENTER.

**Let us obtain descriptive statistics on our data set.**

Press STAT, then arrow over to CALC.
Choose 1-Var Stats. Supply L_{1}
as the argument by typing <2^{nd}>L_{1}.
Press ENTER.

Scroll down to view all of the results.

It should be noted that the TI-83 method for obtaining the quartiles is different than the by-hand position point formulas in the textbook (see page 15). Neither method is "wrong," but students should be aware of this discrepancy.

**Now let us get a histogram of our data.**

Press <2^{nd}>STAT PLOT.
Note that there are three plots you can specify for display (all at once if you wish!)

Choose Plot1. Change it from Off to On.

There are six types of plots to choose from. Move the cursor over to the third one in the first row. This is a histogram. Press ENTER.

The argument for Xlist should be
L_{1}, the list containing our data. If we had any frequency
counts in another data list, this would need to be entered for Freq.
This is not the case for our example, so leave it as "
1", the default.

Once this is done, press GRAPH. You may need to make some adjustments before the plot will show up on the screen. A good way to get a quick viewing window appropriate for the data and for the plot type selected is ZoomStat: Press ZOOM, then choose 9:ZoomStat.

If this does not result in an adequate graph, press WINDOW to see some of the specifications. For a histogram, Xscl is the width of the intervals.

While viewing the histogram, pressing TRACE will allow you to get more information out of the graph. For example, the image above shows that the second rectangle, which represents the interval [21, 30), contains two observations.

Move the cursor left and right to get information on each interval.

**Finally, let us obtain a boxplot for our data.**

Turn the histogram, Plot1, Off. Choose Plot2. Turn it On.

Move the cursor to the right until you get to the second row of plot choices.

There are two kinds of boxplots to choose from. The one in the middle is a "simple" boxplot, the same kind that is described in the textbook, and the same kind that is produced by Excel, although Excel displays boxplots in a vertical manner.

The one to the left is a "modified" boxplot. This graph uses a symbol to mark "outliers," i.e., unusually small or large data points. This is a more informative plot, but in the spirit of consistency, let us stick with the simple boxplot.

Again, Xlist should be
L_{1}, and
Freq should be the default,
1.
Make sure that Plot2 is the only
plot turned On. Press GRAPH.

While viewing the boxplot, press TRACE. This will allow you to scroll through the five number summary. For example, the image above shows that the third quartile is 34.