The Open Door Web Site : IB Biology : ICT in Biology : Statistics continued

You will also find it useful to see the distribution of your data as a frequency histogram. This too can be carried out on the calculator.

Open STAT PLOT and select Plot1
Switch it to On by pressing

.
Under Type: select the histogram type of presentation.
Scroll to Xlist: and select the list you want to plot. Press

then

then scroll down to the list of data. Press

.
There is no Ylist because the histogram plots the frequency of the different data in the Xlist in regular groups called class intervals. These are set automatically by the calculator.
Press

then

and the histogram will appear.

To adjust your histogram press and enter the following information:
Xmin is the lower limit of the lowest class interval
Xmax is the upper limit of the highest class interval
Xscl is the width of the class intervals
Ymin set zero
Ymax needs to be higher than the highest frequency
Yscl and Xres can be left as the default values
When these are set press and inspect the histogram. If you want to adjust the histogram. If you want to adjust the histogram further press again and change the values.

If you want to see if the histogram approaches a normal distribution you may test this using the normal probability graph. This is the last type of graph in the STAT PLOT series.

Return to STAT PLOT and Plot 1. Scroll to Type: Then scroll through the list to the last one and press .

Press then . The graph that appears now will be a scattergram of points. If they fall into a diagonal line, the distribution of the data follows a normal distribution.