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PHP : Function Reference : Statistics Functions : stats_standard_deviation

# stats_standard_deviation

## Returns the standard deviation (PECL stats:1.0.0-1.0.2) float stats_standard_deviation ( array a [, bool sample] )

Warning:

This function is currently not documented; only the argument list is available.

a
sample

## Code Examples / Notes » stats_standard_deviation

kotecky o hotmail o com

Missing standard deviation calculated from a population (division by N or by N-1): http://en.wikipedia.org/wiki/Standard_deviation

mightymrj

Here's a couple functions I made that easily calculate the standard deviation.
function average(\$array){
\$sum   = array_sum(\$array);
\$count = count(\$array);
return \$sum/\$count;
}
//The average function can be use independantly but the deviation function uses the average function.
function deviation (\$array){

\$avg = average(\$array);
foreach (\$array as \$value) {
\$variance[] = pow(\$value-\$avg, 2);
}
\$deviation = sqrt(average(\$variance));
return \$deviation;
}
I hope this is useful

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stats_absolute_deviation
stats_cdf_beta
stats_cdf_binomial
stats_cdf_cauchy
stats_cdf_chisquare
stats_cdf_exponential
stats_cdf_f
stats_cdf_gamma
stats_cdf_laplace
stats_cdf_logistic
stats_cdf_negative_binomial
stats_cdf_noncentral_chisquare
stats_cdf_noncentral_f
stats_cdf_poisson
stats_cdf_t
stats_cdf_uniform
stats_cdf_weibull
stats_covariance
stats_den_uniform
stats_dens_beta
stats_dens_cauchy
stats_dens_chisquare
stats_dens_exponential
stats_dens_f
stats_dens_gamma
stats_dens_laplace
stats_dens_logistic
stats_dens_negative_binomial
stats_dens_normal
stats_dens_pmf_binomial
stats_dens_pmf_hypergeometric
stats_dens_pmf_poisson
stats_dens_t
stats_dens_weibull
stats_harmonic_mean
stats_kurtosis
stats_rand_gen_beta
stats_rand_gen_chisquare
stats_rand_gen_exponential
stats_rand_gen_f
stats_rand_gen_funiform
stats_rand_gen_gamma
stats_rand_gen_ibinomial_negative
stats_rand_gen_ibinomial
stats_rand_gen_int
stats_rand_gen_ipoisson
stats_rand_gen_iuniform
stats_rand_gen_noncenral_chisquare
stats_rand_gen_noncentral_f
stats_rand_gen_noncentral_t
stats_rand_gen_normal
stats_rand_gen_t
stats_rand_get_seeds
stats_rand_phrase_to_seeds
stats_rand_ranf
stats_rand_setall
stats_skew
stats_standard_deviation
stats_stat_binomial_coef
stats_stat_correlation
stats_stat_gennch
stats_stat_independent_t
stats_stat_innerproduct
stats_stat_noncentral_t
stats_stat_paired_t
stats_stat_percentile
stats_stat_powersum
stats_variance