Standard Deviation - HP -34C Owner's Handbook Manual

34 Specific Features of the HP-34C
Keystrokes Display
9 -9.0000
35 M 7.0000 Number of data pairs () is
now 7.
DR -21.5714 Average low temperature.
5.2857 Average high temperature.
Standard Deviation
Pressing (] (s])computes the standard deviation (a measure of disper-
sion around the mean) of the accumulated data. The formulas used by the
HP-34C to compute sy, the standard deviation of the accumulated x
values, and sy, the standard deviation of the accumulated y values, are:
= A\ / nZx? — (2x)? o = A\ / n2y* - ()
X nn—1) v nn—1)
These formulas give the best estimates of the population standard
deviations from the sample data. Consequently, the standard devia-
tion given by these formulas is termed by convention the sample
standard deviation.
When you press [n] (s
1. The contents ofthe stack registers are lifted just as they are when
you press (7] (z%), as described on page 30.
2. The standard deviation of the x values (sy) is calculated using the
data accumulated in registers R, (2x?), R; (2x), and R, (n)
according to the formula shown above. The resultant value for sy
appears in the displayed X-register.
3. The standard deviation of the y values (s,) is calculated using the
data accumulated in registers R, (2y?), R; (Zy), and R, (n)
according to the formula shown above. The resultant value forsy
is available in the Y-register.