Errors on errors - Estimating cosmological parameter covariance

Benjamin Joachimi*, Andy Taylor

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Current and forthcoming cosmological data analyses share the challenge of huge datasets alongside increasingly tight requirements on the precision and accuracy of extracted cosmological parameters. The community is becoming increasingly aware that these requirements not only apply to the central values of parameters but, equally important, also to the error bars. Due to non-linear effects in the astrophysics, the instrument, and the analysis pipeline, data covariance matrices are usually not well known a priori and need to be estimated from the data itself, or from suites of large simulations. In either case, the finite number of realisations available to determine data covariances introduces significant biases and additional variance in the errors on cosmological parameters in a standard likelihood analysis. Here, we review recent work on quantifying these biases and additional variances and discuss approaches to remedy these effects.

Original languageEnglish
Pages (from-to)99-103
Number of pages5
JournalProceedings of the International Astronomical Union
Publication statusPublished - 1 Jul 2015


  • cosmological parameters
  • methods: data analysis
  • Methods: statistical


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