Section 3: Numeric Functions 43
Mean
The ’ function computes the arithmetic mean (average) of the x-and y-values
using the accumulated statistics in registers R
1
and R
3
, respectively. When you
press ´’:
1. The contents of the stack registers lift in the same way as if you keyed
in two numbers in sequence. (The mean of x is simultaneously copied
into the X-register as the mean of y is copied into the Y-register.)
2. The mean of the x-values (
x
) is calculated using the statistics
accumulated in R
1
(∑x) and R
0
(n). The mean of the y-values (
y
) is
calculated using the data accumulated in registers R
3
(∑y) and R
0
(n).
The formulas used are shown below:
n
y
y
n
x
x
∑
=
=
Example: From the 5-year statistical data you accumulated (and corrected) in
the preceding examples, calculate the average coal production and electrical
output for the entire period.
Keystrokes Display
´’
6.135
Average electrical output
(average of X-register
inputs) for the 5-year
period.
®
1.832
Average coal production
(average Y-register
inputs) for the 5-year
period.
Retain these statistics in the calculator for use in the next example.
Standard Deviation
Pressing ´S computes the standard deviation (a measure of dispersion
around the mean) of the accumulated statistical data. The formulas used by the
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