Add unit tests.

Author: markrogoyski

src/Statistics/Significance.php

@@ -28,7 +28,7 @@ class Significance
      * @param float $Hₐ Alternate hypothesis (M Sample mean)
      * @param int   $n  Sample size
      * @param float $H₀ Null hypothesis (μ Population mean)
-     * @param float $σ  SD of population (Standard error of the mean)
+     * @param float $σ  SD of population
      *
      * @return array{
      *   z: float,
@@ -61,7 +61,7 @@ public static function zTest(float $Hₐ, int $n, float $H₀, float $σ): array
      * @param float $Hₐ Alternate hypothesis (M Sample mean)
      * @param int   $n  Sample size
      * @param float $H₀ Null hypothesis (μ Population mean)
-     * @param float $σ  SD of population (Standard error of the mean)
+     * @param float $σ  SD of population
      *
      * @return array{
      *   z: float,
@@ -126,7 +126,7 @@ public static function zTestOneSample(float $Hₐ, int $n, float $H₀, float $
      * @param float $μ₁ Sample mean of population 1
      * @param float $μ₂ Sample mean of population 2
      * @param int   $n₁ Sample size of population 1
-     * @param int   $n₂ Sample size of population 1
+     * @param int   $n₂ Sample size of population 2
      * @param float $σ₁ Standard deviation of sample mean 1
      * @param float $σ₂ Standard deviation of sample mean 2
      * @param float $Δ  (Optional) hypothesized difference between the population means (0 if testing for equal means)
@@ -441,7 +441,7 @@ public static function tTestTwoSample(array $x₁, array $x₂): array
      * @param float $μ₁ Sample mean of population 1
      * @param float $μ₂ Sample mean of population 2
      * @param int   $n₁ Sample size of population 1
-     * @param int   $n₂ Sample size of population 1
+     * @param int   $n₂ Sample size of population 2
      * @param float $σ₁ Standard deviation of sample mean 1
      * @param float $σ₂ Standard deviation of sample mean 2
      *

tests/Statistics/SignificanceTest.php

@@ -547,6 +547,27 @@ public function dataProviderFortTestTwoSampleDataSet(): array
                 20.67941, 22.135, 68, 300, 2.820266, 0.9252723,
                 ['t' => -4.205026, 'df' => 70.29978, 'p1' => 0.000076, 'p2' => 7.568864e-05],
             ],
+            // One sample with zero variance (first sample constant)
+            [
+                [10, 10, 10, 10],
+                [8, 10, 12],
+                10, 10, 4, 3, 0, 2,
+                ['t' => 0, 'df' => 2, 'p1' => 0.5, 'p2' => 1],
+            ],
+            // One sample with zero variance (second sample constant)
+            [
+                [8, 10, 12, 14],
+                [10, 10, 10],
+                11, 10, 4, 3, 2.5819888974716, 0,
+                ['t' => 0.7745967, 'df' => 3, 'p1' => 0.24751265, 'p2' => 0.4950253],
+            ],
+            // One sample with zero variance (first sample constant, equal means)
+            [
+                [5, 5, 5, 5, 5],
+                [1, 3, 5, 7, 9],
+                5, 5, 5, 5, 0, 3.162278,
+                ['t' => 0, 'df' => 4, 'p1' => 0.5, 'p2' => 1],
+            ],
         ];
     }