Still celebrating National IT Professionals Day with 3 months of free Premium Membership. Use Code ITDAY17

x
?
Solved

Calculate uncertainty

Posted on 2014-04-07
4
Medium Priority
?
293 Views
Last Modified: 2014-04-09
Hello Experts:

I need some assistance with applying a formula/equation (based on calculating "uncertainty".

As the saying goes "A picture is worth a thousand words", I've attached a spreadsheet that contains the following:

1. Calculation of sound in sea water (this is complete)
2. Reference to website that includes equations for "uncertainty"

Based on step #2, I need to calculate the value for uncertainty based on a) multiple inputs and b) single input.

Given the listed equations (on NIST's website), how to I calculate a) and b) in MS-Excel?

Thank you in advance,
EEH
Calculate-uncertainty.xlsx
0
Comment
Question by:ExpExchHelp
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
  • 2
4 Comments
 
LVL 20

Accepted Solution

by:
GrahamMandeno earned 2000 total points
ID: 39984045
Hi EEH

Not really my field, but it seems clear to me that u(xN) is the uncertainty in the measurement of xN, not the measurement itself.

For example, if your temperature estimate is (2 ± 0.5) °C, then u(T) is 0.5.

It seems that you multiply these by the squares of the constants in the original formula, so the first term a1^2*u(x1)^2 is:

4.591^2 * 0.5^2

I'm not sure what happens when the estimated value is raised to a power, as in the terms like (5.304*10^-2)*(T^2)

It's even trickier when they are exponentiated and multiplied:
(7.139*10^-13)*T*(D^3)

All the best,
Graham
0
 

Author Comment

by:ExpExchHelp
ID: 39984335
Graham:

How did you arrive at 4.591?  

=2.05^2 = 4.2025... multiplying it by 0.5^2 doesn't give me the value either.

Would you be ok to send me your version of the spreadsheet w/ these calculations?

Thanks,
EEH
0
 
LVL 20

Expert Comment

by:GrahamMandeno
ID: 39989450
Hi EEH (what's your real name, by the way?  :)

Thanks for awarding the points.  I'm puzzled because I posted a followup answer to your question 24 hours ago and it seems to have disappeared.

The 4.591 is the coefficient of the first non-constant term in the Mackenzie formula:

1448.96 + 4.591T - ...

As I understand the article on combined uncertainty, it is therefore the a1 in the term:
a1^2*u(x1)^2
and u(x1) is the uncertainty of T.

I don't have my own version of the spreadsheet, sorry.  I just took a peek at your copy.

All the best,
Graham
0
 

Author Comment

by:ExpExchHelp
ID: 39989820
Graham:

Thanks... appreciate the additional feedback.    ;)

Cheers,
Tom
0

Featured Post

Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

You need to know the location of the Office templates folder, so that when you create new templates, they are saved to that location, and thus are available for selection when creating new documents.  The steps to find the Templates folder path are …
Access developers frequently have requirements to interact with Excel (import from or output to) in their applications.  You might be able to accomplish this with the TransferSpreadsheet and OutputTo methods, but in this series of articles I will di…
This Micro Tutorial demonstrate the bugs in Microsoft Excel for Mac with Pivot Charts.
This Micro Tutorial will demonstrate on a Mac how to change the sort order for chart legend values and decrpyt the intimidating chart menu.

722 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question