Re^2: Excel or Perl for simple statistics?

[Anonymous Monk]

Yes, I also see the standard error but this is like 0.0896196283 or something, nothing close to 0.41 or 0.401.
My question is, would you use the Perl module or just stick with Excel?

[pryrt]

I believe davies was wrong about it also being called the standard error: according to wp, Standard_error, the standard error is the standard deviation divided by the root of the number of samples.

The population standard deviation (Excel: =STDEVP() or =STDEV.P()) assumes you that have data for the entire population; the sample standard deviation (Excel: =STDEV() or =STDEV.S()) assumes that your n data points are just a sample of the population, so it uses a different denominator (n-1) inside the radical, to account for the uncertainty because it's just a sample, not the whole population. Given your set of data, the 0.401791 is the population standard deviation, and the 0.410689 is the sample standard deviation.

• Population standard deviation: σ = sqrt( Σ{ (x_i - x_avg)² } / { n } )
• Sample standard deviation: s = sqrt( Σ{ (x_i - x_avg)² } / { n - 1 } )

According to Statistics::Basic, you can set $Statistics::Basic::UNBIAS true to get the sample, or (implied) set it false to get the population. Statistics::Lite directly says that their stddev() function is the unbiased (sample) n-1, which matches the Excel =STDEV() function, and they have the stddevp() for the population n, matching the Excel =STDEVP().

[Anonymous Monk]

Ok, so problem seems to be fixed if I use Statistics::Lite module instead...
Do you think it could be associated to the fact that with Statistics::Lite I pass the numbers as array instead of array reference that I was using in Statistics::Basic
My list was:


0.964
0
0
0.94
0.895
0.915
0.775
0.868
0
0.796
0.866
0.819
0
0
0
0
0.794
0.806
0.781
0.807
0.783

[poj]

.. as array instead of array reference ..

I get the same either way and no difference with Excel

#!perl
use strict;
use Statistics::Basic 'stddev';

my @data = (0.964, 0, 0, 0.94, 0.895,
0.915, 0.775, 0.868, 0, 0.796, 0.866,
0.819, 0, 0, 0, 0, 0.794, 0.806,
0.781, 0.807, 0.783);
print stddev(\@data)+0;
print "\n";
print stddev(@data)+0;
# 0.400791162022762
 
# excel 
# STDEVP 
# Calculates standard deviation based 
# on the entire population given as arguments.
# 0.400791162

poj