diff --git a/.gitignore b/.gitignore
index 3e7e415..d6fd42d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -26,3 +26,4 @@ tags
 mtrace-test
 mtrace-test.trace
 mtrace-test.txt
+av-variance
diff --git a/Makefile b/Makefile
index d0d6529..9ed1d75 100644
--- a/Makefile
+++ b/Makefile
@@ -2,7 +2,7 @@ CFLAGS=-std=c99 -Wextra -pedantic -g -O2
 
 CFLAGS=-std=c99 -Wextra -pedantic -g -O0
 
-TARGETS=approximate-pi linked-list mandelbrot threads circular-buffer structs ncurses-pong bit-fuckery bit-fuckery2 checkcheck multibrot bloom wo-lernen lua-foo binsearch test-inline-assembly uiowa-threads-example mtrace-test
+TARGETS=approximate-pi linked-list mandelbrot threads circular-buffer structs ncurses-pong bit-fuckery bit-fuckery2 checkcheck multibrot bloom wo-lernen lua-foo binsearch test-inline-assembly uiowa-threads-example mtrace-test av-variance
 EXTRAS=mandelbrot.bmp multibrot.png test-inline-assembly.s tags mtrace-test.trace mtrace-test.txt
 
 .PHONY: all
diff --git a/av-variance.c b/av-variance.c
new file mode 100644
index 0000000..7bfabd0
--- /dev/null
+++ b/av-variance.c
@@ -0,0 +1,39 @@
+#include <stdio.h>
+#include <stdbool.h>
+#include <assert.h>
+#include <math.h>
+
+double mean(double set[], int set_n) {
+  double sum = 0.0;
+  for(int i=0; i<set_n; i++) {
+    sum += set[i];
+  }
+
+  return sum/set_n;
+}
+
+bool isalmost(double x, double c, double epsilon) {
+  assert(epsilon >= 0.0);
+  return fabs(x-c) < epsilon;
+}
+
+int main() {
+  // Some data
+  double d[] = {7, 8, 5, 1, 6, 2};
+  const int d_n = 6;
+
+  double e[] = {-10, 0, 10, 11, 12, 13, 14, 8, 9, 10, 11, 10, 10};
+  const int e_n = 13;
+
+  // Some tests
+  assert(isalmost(mean(d, d_n), 4.833, 0.001));
+  assert(isalmost(mean(e, e_n), 8.307, 0.001));
+
+  // XXX assert(isalmost(median(d, d_n), 5.5, 0.001));
+  // XXX assert(isalmost(median(e, e_n), XXX, 0.001));
+  // XXX Variance
+  // XXX Stddev
+  // XXX Range
+  // XXX Mode
+  // XXX Percentile
+}