
Registering columns as ‘in use’
Working with frequency tables
Auto scale
x
i
Change into the
SYMB
view and edit yours so that it looks like the one
on the right. You must make sure that
H2
is
ed, because only
checked columns will show in the
view.
Note that a screen key is provided to give you the letter
C
without
having to use the
ALPHA
key.
to
see them.
The stats are should now be available for both columns of data. Return to the
NUM
view and press
As an alternative to the method used above, you could also have
created a ‘virtual’ column of data by using the
SYMB
view. Simply
enter an expression giving the new column as a function of the old one.
Although the ‘virtual’ column will not be displayed in the
NUM
view (and
does not consume memory), it can now be graphed and analyzed
statistically.
You may be wondering why the
SYMB
view is organized around histograms
H1, H2..H0
rather than simply
around the columns
C1, C2..C0
. The reason is that it allows you to easily cope with a frequency table by
setting up one column to represent values and another to represent the frequencies. If you are not using a
frequency table then the frequencies are normally set, by default, to 1 as can be seen on the previous page.
So how do we deal with frequency tables? Let's set up columns
C3
and
C4
to represent the table below.
freq.
Enter the values
3, 4, 5, 6, 7 and 8 into
C3
12
and then 12, 19, 25, 37, 15 and 9 into
C4
.
19
25
Now set up your
SYMB
view to look
37
like the one right. Make sure only
H3
is
15
checked. You can, if you wish, delete the
9
definitions for
H1
and
H2
but make sure
they are not
ed.
3
4
5
6
7
8
The reason for the last instruction is that only one histogram can be drawn at a time and if more than one data
set is
ed then only the first one is drawn.
Now use
VIEWS
Auto Scale
to plot the graph. You will hopefully find
that it looks like the one on the right. The
Auto Scale
function is always
very effective in the Statistics aplet and is recommended.
116