9 Statistics
To enter statistical data we use the function
Σ+
. For one variable statistic just enter the number and
press Σ+. For two variables statistic first enter y, press ENTER and then enter x (without pressing
ENTER!) and finally press Σ+.
To clear statistic data just do
▀ CLEAR CLΣ
.
The statistical functions are available in
▀ STAT
menu and they are:
Σ+:
The same of pressing
Σ+.
SUM
: Calculates the sum of the statistical data.
MEAN
: Calculates the mean of the statistical data.
WMN
: Calculates the weighted mean (
x
weighted by
y
).
SDEV
: Sample standard deviation. (To calculate the Population standard deviation you must
calculate the mean, add it to statistical data and then press SDEV)
CFIT
: This is a sub-menu to fit the data in linear regression, logarithm regression,
exponential regression or power regression.
There is also a second line with
ALL
,
LINΣ
,
ΣREG
and
ΣRG?
Functions.
Example: A particle of mass
m
1
=1kg is at the position
x
1
=2m while a particle of mass
m
2
=3kg is at
position
x
2
=6m. What is the position of the center of the mass?
Solution: The position of the center of the mass is given by
x
cm
=
x
1
m
1
x
2
m
2
m
1
m
2
This is a weighted mean where the physical mass is the statistical weight.
To calculate it using HP-42S we do:
▀
CLEAR CLΣ
(cleaning statistical data)
1 (This is
m
1
)
ENTER
2 (This is
x
1
)
Σ+
3
ENTER
6
Σ+
▀
STAT WMN
Which gives to us 5.
9.1 The sub-menu
CFIT
.
The CFIT menu has the following functions:
FCSTX
,
FCSTY
,
SLOPE
,
YINT
,
CORR
,
MODL
.
