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Chapter 16: Statistics and Data Plots 263
16STATS.DOC TI-89/TI-92 Plus: Statistics and Data Plots (English) Susan Gullord Revised: 02/23/01 1:12 PM Printed: 02/23/01 2:17 PM Page 263 of 22
Statistical variables are stored as system variables. However,
regCoef
and
regeq
are treated as a list and a function variable, respectively.
One
Var
Two
Var Regressions
mean of x values
üü
sum of
x
values
G
x
G
x
sum of
x
ñ
values
G
x
ñ
G
x
ñ
sample std. deviation of
xSxSx
population std. deviation of
x
†
s
x
s
x
number of data points
nStat nStat
mean of
y
values
ÿ
sum of
y
values
G
y
sum of
y
ñ
values
G
y
ñ
sample standard deviation of
ySy
population std. deviation of
y
†
s
y
sum of
x
ù
y
values
G
xy
minimum of
x
values
minX minX
maximum of
x
values
maxX maxX
minimum of
y
values
minY
maximum of
y
values
maxY
1st quartile
q1
median
medStat
3rd quartile
q3
regression equation
regeq
regression coefficients (
a
,
b
,
c
,
d
,
e
)
regCoef
correlation coefficient ††
corr
coefficient of determination ††
R
ñ
summary points
(MedMed only) †
medx1, medy1,
medx2, medy2,
medx3, medy3
† The indicated variables are calculated but are not shown on the
STAT VARS
screen.
††
corr
is defined for a linear regression only;
R
ñ
is defined for all
polynomial regressions.
Statistical Variables
Statistical calculation results are stored to variables. To access
these variables, type the variable name or use the VAR-LINK
screen as described in Chapter 21. All statistical variables are
cleared when you edit the data or change the calculation type.
Other conditions that clear the variables are listed on
page 260.
Calculated Variables
Tip: If regeq is 4x + 7, then
regCoef is {4 7}. To access
the “a” coefficient (the 1st
element in the list), use an
index such as regCoef[1].
Note: 1st quartile is the
median of points between
minX and medStat, and 3rd
q
uartile is the median of points
between medStat and maxX.
To type the character
G
,
press:
TI
-
89
:
¥c
¤
[S]
TI
-
92 Plus:
2
G
¤
S
To type the character
s
,
press:
TI
-
89:
¥c
j
[S]
TI
-
92 Plus
:
2
G S
Tip: To type a power (such
as 2 in
G
x
ñ
),
ü
, or
ý
,
press
2¿
and select it from
the
Math
menu.