Return-Path: william@bourbon.usc.edu
Delivery-Date: Tue Sep 12 17:00:51 2006
X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on merlot.usc.edu
X-Spam-Level:
X-Spam-Status: No, score=-0.9 required=5.0 tests=ALL_TRUSTED,AWL,NO_REAL_NAME
autolearn=ham version=3.1.3
Received: from bourbon.usc.edu (bourbon.usc.edu [128.125.9.75])
by merlot.usc.edu (8.13.5/8.13.5) with ESMTP id k8D00phB026099
for ; Tue, 12 Sep 2006 17:00:51 -0700
Received: from bourbon.usc.edu (localhost.localdomain [127.0.0.1])
by bourbon.usc.edu (8.13.5/8.13.5) with ESMTP id k8CNvIfb023240
for ; Tue, 12 Sep 2006 16:57:18 -0700
Received: (from william@localhost)
by bourbon.usc.edu (8.13.5/8.13.5/Submit) id k8CNvIJa023239
for cs551@merlot; Tue, 12 Sep 2006 16:57:18 -0700
Date: Tue, 12 Sep 2006 16:57:18 -0700
From: william@bourbon.usc.edu
Message-Id: <200609122357.k8CNvIJa023239@bourbon.usc.edu>
To: cs551@merlot.usc.edu
Subject: standard deviation...
Hi,
Let X be something you are measuring. The square of the
standard deviation of X is called the variance of X. One
simple way to calculate the variance of X is:
variance(X) = average(X^2) = average(X)^2
where a^2 means a squared. To calculate average(X^2),
just pretend you are measuring Y which is simply X^2.
--
Bill Cheng // bill.cheng@usc.edu