254
T
T
h
h
e
e
‘
‘
S
S
t
t
a
a
t
t
-
-
T
T
w
w
o
o
’
’
g
g
r
r
o
o
u
u
p
p
o
o
f
f
f
f
u
u
n
n
c
c
t
t
i
i
o
o
n
n
s
s
PREDY(x-val)
This function predicts the y value for a pair of columns set up as bivariate
data in the Statistics aplet. This is discussed in more detail in the section
covering the Statistics aplet, but a brief summary will be given here.
It assumes that:
(i) the bivariate data is entered into a pair of columns (eg.
C1
and
C2
, with
C1
containing the independent data and
C2
the dependent data),
and
(ii) that these two columns have been specified in the
SYMB
view to be paired
bivariate data,
and
(iii) that this data set has been graphed in the
PLOT
view and that the
FIT
screen
key has been used to plot the line of best fit for the pair of columns,
If these conditions are satisfied then the
function
PREDY(3.5)
will produce a predicted
y (dependent) value for the x (indep.) value of
3 5
⋅
.
Calculator Tip
The line of best fit used in the function
PREDY
is whichever
one was last plotted.
It is up to you
to ensure that this is in
fact the one you want used! It is far easier and more
reliable to use the facilities provided in the
PLOT
view (see
PREDY
values.
PREDX(y-val)
The
PREDX
function simply reverses the line of best fit. For example, the
equation
ˆ
0 8199
1 1662
Y
X
= ⋅
+ ⋅
earlier would use
(
1.1662)
ˆ
0.8199
Y
X
−
=
to predict
the X values.
Note:
See page 146 for important information on this function.