Bibcode
de Diego, J. A.
Bibliographical reference
The Astronomical Journal, Volume 148, Issue 5, article id. 93, 16 pp. (2014).
Advertised on:
11
2014
Citations
42
Refereed citations
42
Description
Microvariations probe the physics and internal structure of quasars.
Unpredictability and small flux variations make this phenomenon elusive
and difficult to detect. Variance-based probes such as the C and F
tests, or a combination of both, are popular methods to compare the
light curves of the quasar and a comparison star. Recently, detection
claims in some studies have depended on the agreement of the results of
the C and F tests, or of two instances of the F-test, for rejecting the
non-variation null hypothesis. However, the C-test is a non-reliable
statistical procedure, the F-test is not robust, and the combination of
tests with concurrent results is anything but a straightforward
methodology. A priori power analysis calculations and post hoc analysis
of Monte Carlo simulations show excellent agreement for the analysis of
variance test to detect microvariations as well as the limitations of
the F-test. Additionally, the combined tests yield correlated
probabilities that make the assessment of statistical significance
unworkable. However, it is possible to include data from several field
stars to enhance the power in a single F-test, increasing the
reliability of the statistical analysis. This would be the preferred
methodology when several comparison stars are available. An example
using two stars and the enhanced F-test is presented. These results show
the importance of using adequate methodologies and avoiding
inappropriate procedures that can jeopardize microvariability
detections. Power analysis and Monte Carlo simulations are useful tools
for research planning, as they can demonstrate the robustness and
reliability of different research approaches.