HP 12C - Covariance

117
3. Repeat step 2 for each new case.
Example: Find Q(x) for x = 1.18 and x = 2.1.
Covariance
Covariance is a measure of the interdependence between paired
variables (x and y). Like standard deviation, covariance may be defined
for either a sample (S
xy
) or a population (S'
xy
) as follows:
S
xy
= r * s
x
* s
y
S'
xy
= r * s'
x
* s'
y
The following procedure finds the covariance of a sample (S
xy
) and of a
population (
S'
xy
):
1. Press CLEAR .
2. Key in the y-values and press .
3. Key in the
x-values and press . Repeat steps 2 and 3 for all data
pairs.
4. Press to obtain the value of S
xy
.
5. Press 1 1 1 to obtain S'
xy
.
Example 1: Find the sample covariance (S
xy
) and population covariance
(
S'
xy
) for the following paired variables:
Keystrokes Display
1.18
0.12 Q(1.18)
2.1
0.02 Q(2.1)
x
i
26 30 44 50 62 68 74
y
i
92 85 78 81 54 51 40
Keystrokes Display
CLEAR
92 26
85 30
78 44
81 50
7.00 Total number of entries.