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Centro de Astrofísica da Universidade do Porto

Modified Median Statistics and Type Ia Supernova Data

P. P. Avelino, C. J. A. P. Martins, P. Pinto

The median statistic has recently been discussed by Gott et al. as a more reliable alternative to the standard χ2 likelihood analysis, in the sense that it requires fewer assumptions about the data and is almost as constraining. We apply this statistic to the combined data set of 92 distant Type Ia supernovae currently available and also to a mock SNAP-class data set. We find that the performances of the modified median and χ2 statistics are comparable, particularly in the latter case. We further extend the work of Gott et al. by modifying the median statistic to account for the number and size of sequences of consecutive points above or below the median. We also comment on how the performance of the statistic depends on the choice of free parameters that one is estimating.

The Astrophysical Journal
Volume 575, Page 989
August 2002

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Institute of Astrophysics and Space Sciences

Institute of Astrophysics and Space Sciences (IA) is a new but long anticipated research infrastructure with a national dimension. It embodies a bold but feasible vision for the development of Astronomy, Astrophysics and Space Sciences in Portugal, taking full advantage and fully realizing the potential created by the national membership of the European Space Agency (ESA) and the European Southern Observatory (ESO). IA resulted from the merging the two most prominent research units in the field in Portugal: the Centre for Astrophysics of the University of Porto (CAUP) and the Center for Astronomy and Astrophysics of the University of Lisbon (CAAUL). It currently hosts more than two-thirds of all active researchers working in Space Sciences in Portugal, and is responsible for an even greater fraction of the national productivity in international ISI journals in the area of Space Sciences. This is the scientific area with the highest relative impact factor (1.65 times above the international average) and the field with the highest average number of citations per article for Portugal.

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