Abstract
It is shown that if (X 1, X 2, . . . , X n ) is a random vector with a logconcave (logconvex) joint reliability function, then X P = mini∈P X i has increasing (decreasing) hazard rate. Analogously, it is shown that if (X 1, X 2, . . . , X n ) has a logconcave (logconvex) joint distribution function, then X P = maxi∈P X i has decreasing (increasing) reversed hazard rate. If the random vector is absolutely continuous with a logconcave density function, then it has a logconcave reliability and distribution functions and hence we obtain a result given by Hu and Li (Metrika 65:325–330, 2007). It is also shown that if (X 1, X 2, . . . , X n ) has an exchangeable logconcave density function then both X P and X P have increasing likelihood ratio.
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The work of J. Navarro was partially supported by Ministerio de Ciencia y Tecnologí a under grant BFM2003-02947 and Fundación Séneca under grant 00698/PI/04.
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Navarro, J., Shaked, M. Some properties of the minimum and the maximum of random variables with joint logconcave distributions. Metrika 71, 313–317 (2010). https://doi.org/10.1007/s00184-009-0232-9
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DOI: https://doi.org/10.1007/s00184-009-0232-9