# HP F2226A - 48GII Graphic Calculator User Manual Page 582

Graphing calculator.

To obtain the data fitting press @@OK@@.
shown below for our particular data set, consists of the following three
lines in RPN mode:
3: '0.195238095238 + 2.00857142857*X'
2: Correlation: 0.983781424465
1: Covariance: 7.03
Level 3 shows the form of the equation. In this case, y = 0.06924 + 0.00383
x. Level 2 shows the sample correlation coefficient, and level 1 shows the
covariance of x-y.
Definitions
For a sample of data points (x,y), we define the sample covariance as
s
The sample correlation coefficient for x,y is defined as
Where s
, s
are the standard deviations of x and y, respectively, i.e.
x
y
1
2
s
=
x
n
1
The values s
and r
are the "Covariance" and "Correlation," respectively,
xy
xy
obtained by using the "Fit data" feature of the calculator.
Linearized relationships
Many curvilinear relationships "straighten out" to a linear form. For example,
the different models for data fitting provided by the calculator can be
linearized as described in the table below.
The output from this program,
1
n
=
(
x
x
)(
xy
i
n
1
i
=
1
s
xy
r
.
xy
s
s
x
y
n
2
2
(
x
x
)
s
=
i
y
i
=
1
y
y
)
i
1
n
2
(
y
y
)
i
n
1
i
=
1
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