Uncertainty of coefficients after a least square fit

Click For Summary
SUMMARY

The discussion focuses on calculating the uncertainty of coefficients a0 and a1 after performing a least squares fit on a linear function (y=a0+a1*x). It is established that the diagonal elements of the covariance matrix C represent the square of the uncertainties for each coefficient when off-diagonal elements are absent. However, when off-diagonal elements are present, they affect the uncertainty of expressions involving both coefficients. A reference to Eq 22 of Kirchner's note is highlighted as a valuable resource for understanding this concept.

PREREQUISITES
  • Understanding of least squares fitting
  • Familiarity with covariance matrices
  • Knowledge of linear regression coefficients
  • Basic statistics concepts related to uncertainty
NEXT STEPS
  • Review the derivation of covariance matrices in linear regression
  • Study the implications of off-diagonal elements in uncertainty calculations
  • Examine Eq 22 of Kirchner's note for detailed insights
  • Learn about advanced statistical methods for estimating uncertainties
USEFUL FOR

Statisticians, data analysts, and researchers involved in linear regression analysis and uncertainty quantification in model fitting.

sth
Messages
2
Reaction score
0
Fitting data to a linear function (y=a0+a1*x) with least square gives the coefficients a0 and a1. I am having trouble with calculating the uncertainty of a0. I understand that the diagonal elements of the covariance matrix C is the square of the uncertainty of each coefficient if there are no off-diagonal elements. But what is the uncertainty of a0 if there are off-diagonal elements?
 
Physics news on Phys.org
Hello sth, :welcome:

Found your answers and a good reference in this thread

[edit] on second thought: the errors are the diagonal elements. The off-diagonal elements come in when you evaluate expressions where both coefficients appear and you want the uncertainty in the result.
 
Hi BvU,
Thank you for welcoming and the reference. Seems like Eq 22 of Kirchner's note is what I was looking for.
 

Similar threads

  • · Replies 28 ·
Replies
28
Views
3K
  • · Replies 14 ·
Replies
14
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 7 ·
Replies
7
Views
2K
Replies
24
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 16 ·
Replies
16
Views
2K
  • · Replies 6 ·
Replies
6
Views
16K