My Math Forum  

Go Back   My Math Forum > College Math Forum > Advanced Statistics

Advanced Statistics Advanced Probability and Statistics Math Forum


Reply
 
LinkBack Thread Tools Display Modes
February 18th, 2009, 05:57 PM   #1
Newbie
 
Joined: Feb 2009

Posts: 1
Thanks: 0

weight of variances in 2 values on overall variance

Hello,

I've been having a heck of a time today trying to find the answer to this question. If you have variances in 2 values which are contributing to an overall variance, how do you determine the percentage of the overall variance the variance in each value comprises? For example....

If I expect to see 300 clients in 100 staff hours per week, I have a target efficiency of 3 clients/staff hour. However, in one particular week I see only 250 clients with 125 staff hours. My efficiency for this period is only 2 clients/staff hour. My overall efficiency is down 33% to target. My clients are down 16.67% and my staff hours are over by 25%. How do I determine what percentage of the 33% decrease in efficiency is attributable to increased staff hours and which is attributable to decreased clients?

It seemed like a simple thing until I tried to sit down and figure it out, and I'm sure it's encountered all the time in looking at efficiency numbers in all kinds of business applications, but for the life of me I just can't figure out the formula to use to determine this. I'm hoping someone here can help me out. Thank you in advance for your assistance.

Edit: Found a solution today. In the example above, 16.67x + 25x = 33, x=33/41.67, x=.7919, 13.2 + 19.8 = 33, 13.2/33 = 40% & 19.8/33 = 60%
SpruceGoose is offline  
 
Reply

  My Math Forum > College Math Forum > Advanced Statistics

Tags
values, variance, variances, weight



Thread Tools
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
Arrive specific place time with variance 0 u r neg variance BenFRayfield Complex Analysis 0 January 20th, 2014 05:42 AM
Help with data pooling (Means and variances) kylonewton Algebra 0 April 10th, 2013 11:46 AM
Expected values and variance question. latortuga Advanced Statistics 2 June 14th, 2011 04:13 PM
T-test in multiple variances hailholyghost Advanced Statistics 0 March 27th, 2011 05:20 PM
Weighted variances. xnull Algebra 2 February 23rd, 2009 11:42 PM





Copyright © 2019 My Math Forum. All rights reserved.