HP 39gs_40gs_Mastering The Graphing Calculator_English_E_F2224-90010

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.
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