/**
* Compute the p-value of null-hypothesis holds.
*
* Warning: please read
* http://en.wikipedia.org/wiki/P-value#Frequent_misunderstandings
* or consult statistician how to interpret results.
*
* @param int $degreesOfFreedom If you have 1-D histogram
* analysis, $degreesOfFreedom should be number of bins-1.
* For other scenarios, please consult statistician.
* @param double $chisqr result of chi-square test
*
* @returns double p-value.
*/
static function pvalue($degreesOfFreedom, $chisqr)
{
Preconditions::check(is_int($degreesOfFreedom));
Preconditions::check($degreesOfFreedom > 0);
Preconditions::checkIsNumber($chisqr);
Preconditions::check($chisqr >= 0);
return Gamma::regularizedGammaQ($degreesOfFreedom / 2.0, $chisqr / 2.0);
}
public function testRegularizedGammaPositivePositive2()
{
$this->assertEquals(0.05265301734, Gamma::regularizedGammaP(5.0, 2.0), '', 1.0E-8);
$this->assertEquals(1 - 0.05265301734, Gamma::regularizedGammaQ(5.0, 2.0), '', 1.0E-8);
}
