Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Undesirable effects of covariance matrix techniques for error analysis   Regression with $\chi^2$ constructed from the covariance matrix should not be
used for some combinations of covariance matrices and fitting functions. Using
the technique for unsuitable combinations can amplify systematic errors. This
amplification is uncontrolled, and can produce arbitrarily inaccurate results
that might not be ruled out by a $\chi^2$ test. In addition, this technique can
give incorrect (artificially small) errors for fit parameters. I give a test
for this instability and a more robust (but computationally more intensive)
method for fitting correlated data.

3
The categories of this paper are: physics
30
The categories of this paper are: q-alg
27
The categories of this paper are: comp-gas
2
The categories of this paper are: math
21
The categories of this paper are: adap-org
23
The categories of this paper are: solv-int
22
The categories of this paper are: chao-dyn
28
The categories of this paper are: alg-geom
37
The categories of this paper are: supr-con
31
The categories of this paper are: ao-sci
24
The categories of this paper are: dg-ga
1
The categories of this paper are: cs
6
The categories of this paper are: astro-ph
19
The categories of this paper are: eess
15
The categories of this paper are: nucl-ex
13
The categories of this paper are: quant-ph