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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 m1=1kg is at the position x1=2m while a particle of mass m2=3kg is at
position x2=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 m1)
ENTER
2 (This is x1)
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.