From b6731184738b6b00923031ae8f6a2c45cc47d294 Mon Sep 17 00:00:00 2001
From: Stephen McQuay <stephen@mcquay.me>
Date: Sun, 23 Nov 2014 00:27:59 -0800
Subject: [PATCH] added simple confidence interval calc

---
 ostat.go | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/ostat.go b/ostat.go
index ecbbad8..002ed27 100644
--- a/ostat.go
+++ b/ostat.go
@@ -95,6 +95,13 @@ func (os *OnlineStat) StdDev() float64 {
 	return math.Sqrt(os.Variance())
 }
 
+func (os *OnlineStat) CI() (float64, float64) {
+	// 95% from http://mathworld.wolfram.com/ConfidenceInterval.html
+	conf := 1.95996
+	dev := os.StdDev() / math.Sqrt(float64(os.n))
+	return os.mean - dev*conf, os.mean + dev*conf
+}
+
 func (os *OnlineStat) String() string {
 	return fmt.Sprintf(
 		"%+v",