Go Back   Science Forums Biology Forum Molecular Biology Forum Physics Chemistry Forum > Molecular Research Topics Forum > Bioinformatics > BioStatistics Forum
Register Search Today's Posts Mark Forums Read

BioStatistics Forum Post Questions and Discuss Biostatistics Programs and Stastistical Analysis Questions


Statistical help required urgently

Statistical help required urgently - BioStatistics Forum

Statistical help required urgently - Post Questions and Discuss Biostatistics Programs and Stastistical Analysis Questions


Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 07-08-2008, 11:30 AM
Pipette Filler
Points: 406, Level: 8 Points: 406, Level: 8 Points: 406, Level: 8
Activity: 0% Activity: 0% Activity: 0%
 
Join Date: Jul 2008
Posts: 2
Thanks: 0
Thanked 0 Times in 0 Posts
Default Statistical help required urgently



Hi all,

I have two absolute quantitation assays that I use to generate a readout of copies of target per pg of input RNA. Both assays generate a standard deviation (each sample is done in triplicate), one in copies per reaction (target assay) and one in pg of RNA per reaction (endogenous assay).

Is there a method of combining the two standard deviations to get an overall error value for the assay? They are different units, so I am uncertain if this is even possible. If it cannot be done this way, is there a statistical conversion I can do to demonstrate any kind of standard error/deviation?

Thanks,

Iain.
Reply With Quote
  #2  
Old 07-08-2008, 06:27 PM
danfive's Avatar
Nobel Laureate
Points: 8,612, Level: 64 Points: 8,612, Level: 64 Points: 8,612, Level: 64
Activity: 0% Activity: 0% Activity: 0%
 
Join Date: Jul 2007
Location: Houston TX
Posts: 969
Thanks: 12
Thanked 184 Times in 154 Posts
Default Re: Statistical help required urgently

I think you want CV.
see ---> [Only registered users see links. ]
I does not combine your two std deviations, instead you will pick one and turn it into percent of the mean.
This makes it more readable to say 55ng + or - 10% instead of 55ng + or - 5.5ng.
Reply With Quote
  #3  
Old 07-10-2008, 08:47 AM
Pipette Filler
Points: 406, Level: 8 Points: 406, Level: 8 Points: 406, Level: 8
Activity: 0% Activity: 0% Activity: 0%
 
Join Date: Jul 2008
Posts: 2
Thanks: 0
Thanked 0 Times in 0 Posts
Default Re: Statistical help required urgently

Hi danfive, thanks for your reply. I am still a bit unsure of this though.

Can i use the mean square error of the two cvs to get an overall standard error for the assay.

As an example,

Sample 1 contains 1e6+/-2e4 copies per reaction of my viral target
Sample 2 contains 1e5+/-3e3 pg of total RNA (GAPDH endogenous QPCR)

I would represent this as 10 copies of target per pg of RNA

Using CV:
The CV for the target assay is (2e4/1e6)*100 = 2%
The CV for the endogenous assay is (3e3/1e5)*100 = 3%

Can I calculate a mean square error using the formula?

mse = sqrt((cv1*cv1)+(cv2*cv2))
= sqrt(4+9)
= 3.0655%

Therefore my result would be 10 copies per pg of total RNA +/- 3.07%


Is this a valid use of mean square error?

Any and all help gratefully received.


Thanks,
Iain.
Reply With Quote
  #4  
Old 07-10-2008, 07:07 PM
danfive's Avatar
Nobel Laureate
Points: 8,612, Level: 64 Points: 8,612, Level: 64 Points: 8,612, Level: 64
Activity: 0% Activity: 0% Activity: 0%
 
Join Date: Jul 2007
Location: Houston TX
Posts: 969
Thanks: 12
Thanked 184 Times in 154 Posts
Default Re: Statistical help required urgently

If I have this right:
Assay 1: Tells you absolute copy number of Target gene
Assay 2: Tells you pg RNA of GAPDH gene

If so you want to use target gene to reference gene normalization.

This may help, read sections for absolute quantification and normalization of expression
---> [Only registered users see links. ]

You may also want to look into this reference on the issue of error bars in experimental biology ---> [Only registered users see links. ]
Reply With Quote
Reply

Tags
required , statistical , urgently


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
statistical analysis jorjor Bioinformatics 0 02-26-2010 04:19 PM
Western blot quantification - improving statistical power lab-rat SDS-PAGE Gel Electrophoresis Forum 1 07-28-2009 05:30 PM
research paper required urgently sheelu Protocols and Methods Forum 1 07-18-2008 02:53 PM
research paper required urgently sheelu Microbiology Forum 0 07-17-2008 11:27 AM
Testing real-time PCR results for statistical significance? Peter Frank Protocols and Methods Forum 2 10-30-2003 09:36 PM


All times are GMT. The time now is 03:57 PM.


Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright 2005 - 2012 Molecular Station | All Rights Reserved
Page generated in 0.13307 seconds with 16 queries