--- oldmath.c	2009-11-01 15:21:19.000000000 -0500
+++ math.c	2009-11-01 15:23:53.000000000 -0500
@@ -61,6 +61,45 @@
     }
 }
 
+/*
+ *  call-seq:
+ *     Math.stdev(array)   =>   double
+ *
+ *  Computes the standard deviation of the elements in an <i>array</i>
+ *  If they are all numbers.
+ *
+ *
+ */
+ 
+static VALUE
+math_stdev(VALUE obj, VALUE ary)
+{		
+	long i;
+	double sum = 0.0;
+	double mean = 0.0;
+	double numer = 0.0;
+	
+	
+	for (i=0; i<RARRAY_LEN(ary); i++) {
+	if( TYPE(RARRAY_PTR(ary)[i]) == T_STRING) {
+		rb_raise(rb_eTypeError, "Element is not a number!");
+	} else {
+		sum = sum +  NUM2DBL(RARRAY_PTR(ary)[i]);
+	}
+	}
+	mean = sum / RARRAY_LEN(ary);
+	
+	for (i=0; i<RARRAY_LEN(ary); i++) {
+	if( TYPE(RARRAY_PTR(ary)[i]) == T_STRING) {
+		rb_raise(rb_eTypeError, "Element is not a number!");
+	} else {
+		numer = numer + pow((NUM2DBL(RARRAY_PTR(ary)[i]) - mean), 2);
+	}
+	}
+	
+	return DBL2NUM(sqrt(numer / RARRAY_LEN(ary)));
+}
+
 
 /*
  *  call-seq: