127
The effect of HRng
The effect of HRange is rather different. It
controls what range of data is analyzed in
calculating the frequencies, and is normally set
automatically to be the maximum and
minimum values for the data. For example H1
(shown right) has an HRange of -2 to 7. If I go
into PLOT SETUP and change this to 0 to 7 then the graph loses the left
hand column representing the value of -2.
The advantage of this is that it allows you to
eliminate outliers from your graph quite easily.
However, eliminating them from your graph
does not eliminate them from inclusion in the
calculation of the values that appear in the
page. To do that you would need to use
DEL in the NUM view to delete the actual data itself.
Grouped data & HWidth
One final note concerns grouped data. We saw earlier how to deal with data
displayed in a frequency table, but did not deal with the case where the data
was also grouped into intervals or classes.
For example, suppose we want to analyze the set of
grouped data in the table on the right.
The hp 39g+ provides some limited methods to deal
with data of this form. Summary statistics can be
obtained by entering the mid-points of the intervals as the data values but
these will only be approximations, as nature of the data itself does not allow
calculation of exact values.
Attempting a normal
PLOT will produce a
series of isolated
columns, each with
width one unit. The
reason for this is that
the calculator is
assuming that there are 14 values of exactly
15 (the mid-point) because it doesn’t realize
that the columns extend the width of the interval 10 - 19.
data freq
10 - 19 14
20 - 29 26
30 - 39 37
40 - 49 23
50 - 59 17
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