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Quadratic regression
Formula for quadratic regression:
•
y
= A + B
x
+ C
x
2
Press
SHIFT
S-SUM
▶
▶
1
to calculate the sum of cubes of
x
data (∑
x
3
)
Press
SHIFT
S-SUM
▶
▶
2
to calculate the sum of the products of
x
-data squares and
y
data (∑
x
2
y
)
Press
SHIFT
S-SUM
▶
▶
3
to calculate the sum of biquadrates of
x
data (∑
x
4
)
Press
SHIFT
S-VAR
▶
▶
3
to calculate regression coeffi cient C
Press
SHIFT
S-VAR
▶
▶
▶
1
to calculate the estimated value of
x
1
(
x
1
)
Press
SHIFT
S-VAR
▶
▶
▶
2
to calculate the estimated value of
x
2
(
x
2
)
Press
SHIFT
S-VAR
▶
▶
▶
3
to calculate the estimated value of
y
(
y
)
•
Example:
Calculate the regression formula coeffi cients for the following data. Calculate the
estimated value of
y
for
x
i
= 9 and the estimated value of
x
for
y
i
= 4.
MODE
MODE
2
(REG)
▶
3
(Quad)
SHIFT
CLR
1
=
2
, 9
DT
4 , 15
DT
6 , 18
DT
8 , 12
DT
10 , 6
DT
Coeffi cient A =
-1.8
SHIFT
S-VAR
▶
▶
1
=
Coeffi cient B =
6.621428571
SHIFT
S-VAR
▶
▶
2
=
Coeffi cient C =
-0.589285714
SHIFT
S-VAR
▶
▶
3
=
y
(if
x
i
=9) =
10.06071429
9
SHIFT
S-VAR
▶
▶
▶
3
=
x
1
(if
y
i
=4) =
0.957544233
4
SHIFT
S-VAR
▶
▶
▶
1
=
x
2
(if
y
i
=4) =
10.2788194
4
SHIFT
S-VAR
▶
▶
▶
2
=
x
y
2
9
4
15
6
18
8
12
10
6