Add Z-Score Algorithm (#3065)

Co-authored-by: Andrii Siriak <siryaka@gmail.com>

src/main/java/com/thealgorithms/maths/StandardScore.java

@@ -0,0 +1,9 @@
+package com.thealgorithms.maths;
+
+public class StandardScore {
+	public static double zScore(double num, double mean, double stdDev)
+	{
+		double z = (num - mean)/stdDev;
+		return z;
+	}
+}

src/test/java/com/thealgorithms/maths/StandardScoreTest.java

@@ -0,0 +1,27 @@
+package com.thealgorithms.maths;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class StandardScoreTest{
+  @Test
+  void test1()
+  {
+    Assertions.assertEquals(StandardScore.zScore(2, 0, 5), 0.4);
+  }
+  @Test
+  void test2()
+  {
+    Assertions.assertEquals(StandardScore.zScore(1, 1, 1), 0.0);
+  }
+  @Test
+  void test3()
+  {
+    Assertions.assertEquals(StandardScore.zScore(2.5, 1.8, 0.7), 1.0);
+  }
+  @Test
+  void test4()
+  {
+    Assertions.assertEquals(StandardScore.zScore(8.9, 3, 4.2), 1.4047619047619049);
+  }
+}