Is there a simpler way??

[yabba]

Ok, I have 6 test grades: 70 74 80 82 68 76 and the average comes out to 75. Now, I need to figure out the standard deviation, which is square root of (sum of squares of these differences)/(class size). I did it this way:

 $std = sqrt((70-75)**2+(74-75)**2+(80-75)**2+
             (82-75)**2+(68-75)**2+(76-75)**2)/6))

Now, if I had a DAT file already containing the scores, $score, and I already have the variable $avg, is there a simpler way??

[repson]

Here is one way I put together where I assume @values to already contain the data from the DAT file mentioned. Code untested.

# compute average
$total += $_ for @values;
$average = $total / @values;

# compute stddev according to your method
$total_deviation += ($_ - $average)**2 for @values;
$standard_deviation = sqrt($total_deviation) / @values;

# compute stddev as I recall it, probably wrong
$total_deviation += abs($_ - $average) for @values;
$standard_deviation = $total_deviation / @values;

[yabba]

Hey, thanks for your help, but I have a question. The @values, what are you referring to?

[jeffa]

You bet. It's called CPAN. Here is a solution with Statistics::Descriptive

use strict;
use Statistics::Descriptive;

my $stat = Statistics::Descriptive::Full->new();
$stat->add_data(70,74,80,82,68,76);

print "mean: ", $stat->mean(), "\n",
      "sum:  ", $stat->sum(), "\n",
      "var:  ", $stat->variance(), "\n",
      "dev:  ", $stat->standard_deviation(), "\n";

Of course, you won't get much credit for this solution on the test. ;)

Jeff

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