HP HP-25 - Page 73

Press Display
[+ 18 10.10 Standard deviation.
If the 10 persons used in the sample were actually the 10
wealthiest persons, the data would have to be considered as a
population rather than as a sample. The relationship between
sample standard deviation (s) and the population standard
deviation (s') is illustrated by the following equation:
Since n is automatically accumulated in register R; when the
data are accumulated by the key, it is a simple matter to con-
vert the sample standard deviation, which has already been
calculated, to population standard deviation.
For example, if the accumulations in registers R, through R,
are still intact from the previous example, you can calculate the
population standard deviation this way:
Press Display
B Sample standard deviation (s).
3 Recalls n.
1[=] Calculates n-I.
N3 (=] Divides n-I by .
B Population standard deviation (s').
Deleting and Correcting Data
If you key in an incorrect value and have not pressed , press
and key in the correct value.
If one of the values is changed, or if you discover after you have
pressed the key that one of the values is in error, you can
correct the summations by using the key as follows:
1. Key the incorrect data pair into the X- and Y- registers.
2. Press [[I []to delete the incorrect data.
3. Key in the correct values for x and y. (If one value of an
X, y data pair is incorrect, both values must be deleted and
reentered.)
4. Press .