Document ID: EPA-HQ-OAR-2002-0051-3528
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2010-09-09T04:00Z

From:
Hector.Ybanez@holcim.com
 To:
Keith Barnett/RTP/USEPA/US@EPA
 Date:
06/18/2010 12:05 PM
 Subject:
Fw: ShortLongTermVariabilityModel.xls

Keith

this is what i being talking about

during our meeting RTI was assuming that variance of means is better
because variances get smaller with time (or as sample size increases) but
that is not true

this attached spreadsheet show how variance change as sample size increases

that is why proportional variance needs to be used

_____________________

Hector Ybanez
Corporate Manager, Environmental
122 West Carpenter Freeway
Suite 485
Irving, Texas 75039
Phone (214) 524 - 2814
Cell (972) 268-1139
Hector.Ybanez@holcim.com
hybanez@gmail.com
www.holcim.com/us
This e-mail is confidential and intended only for the use of the above
named addressee. If you have received this e-mail in error, please delete
it immediately and notify us by e-mail or telephone.
----- Forwarded by Hector Ybanez/USA/Holcim on 06/18/2010 11:00 AM -----
                                                                           
                                                                           
                                                                           
                   Hector                                                  
                   Ybanez/USA/                                             
                   Holcim                                               To 
                                       William Mills                       
                   06/17/2010                                           cc 
                   10:45 AM                                                
                                                                   Subject 
                                       ShortLongTermVariabilityModel.xls   
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           

 fyi

_____________________

Hector Ybanez
Corporate Manager, Environmental
122 West Carpenter Freeway
Suite 485
Irving, Texas 75039
Phone (214) 524 - 2814
Cell (972) 268-1139
Hector.Ybanez@holcim.com
hybanez@gmail.com
www.holcim.com/us
This e-mail is confidential and intended only for the use of the above
named addressee. If you have received this e-mail in error, please delete
it immediately and notify us by e-mail or telephone.
(See attached file: ShortLongTermVariabilityModel.xls)