Merge pull request #3 from msn0/v2

V2

index.js

@@ -0,0 +1,28 @@
+module.exports = function (positiveScore, total) {
+
+    if (total === 0) {
+        return {
+            left: 0,
+            right: 0
+        };
+    }
+
+    // phat is the proportion of successes
+    // in a Bernoulli trial process
+    const phat = positiveScore / total;
+
+    // z is 1-alpha/2 percentile of a standard
+    // normal distribution for error alpha=5%
+    const z = 1.96;
+
+    // implement the algorithm
+    // (http://goo.gl/kgmV3g)
+    const a = phat + z * z / (2 * total);
+    const b = z * Math.sqrt((phat * (1 - phat) + z * z / (4 * total)) / total);
+    const c = 1 + z * z / total;
+
+    return {
+        left: (a - b) / c,
+        right: (a + b) / c
+    };
+};

package.json

@@ -1,6 +1,6 @@
 {
   "name": "wilson-score-interval",
-  "version": "2.0.0",
+  "version": "2.0.1",
   "description": "binomial proportion confidence interval",
   "author": "Michał Jezierski <ambinanitelo@gmail.com>",
   "repository": {