b********e 发帖数: 1796 | 1 Define Phi(x)as the cumulative distribution function of the standard normal
distribution,
c as an arbitrary constant,
How to show log(Phi(x)-log(Phi(x+c)) is concave in x? | s*****9 发帖数: 108 | 2 用这个链接的第二页定理1:(以及第三页的corollary 1)
http://www.unc.edu/~contat/wilsonconcavitynotes.pdf
利用log(phi(x))和log(phi(x+c))都是concave的,然后得到两个相关的不等式组,并
到一起就出来了. | l*********s 发帖数: 5409 | | b********e 发帖数: 1796 | 4 C is positive, sorry to mention that in the OP. |
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