LISTSERV at the University of Georgia
Menubar Imagemap
Home Browse Manage Request Manuals Register
Previous messageNext messagePrevious in topicNext in topicPrevious by same authorNext by same authorPrevious page (May 1999, week 2)Back to main SAS-L pageJoin or leave SAS-L (or change settings)ReplyPost a new messageSearchProportional fontNon-proportional font
Date:         Thu, 13 May 1999 15:28:06 +0100
Reply-To:     John Whittington <medisci@POWERNET.COM>
Sender:       "SAS(r) Discussion" <SAS-L@UGA.CC.UGA.EDU>
From:         John Whittington <medisci@POWERNET.COM>
Subject:      Re: Maximum likelihood estimation
Comments: To: "Berryhill, Timothy" <TWB2@PGE.COM>
Content-Type: text/plain; charset="us-ascii"

At 18:16 11/05/99 -0700, Berryhill, Timothy wrote:

>Seems to me the median is zero. For any theta < 0, f(x) is 0 for all x. >For any positive theta, f(x) is 0 for all negative x and for all x>theta. >If x is distributed uniformly, the median is zero regardless of the value of >theta. >> f(x)=2x/theta**2 , 0<x<theta >> =0, otherwise.

Tim, much as I usually keep away from 'homework' questions, I couldn't help noticing what you'd written! I'm addressing only your comment, not the original question ....

If x is negative (for any theta), then f(x)=0. Similarly, if theta is negative (for any x), then f(x)=0, and, in any event theta**2 must be positive. It therefore follows that f(x) cannot be negative. However, f(x) can have any number of positive values, as well as zero. If f(x) is either zero or positive, but never negative, it seems a bit rash to suggest that the median is inevitably zero. I'm not saying (without considering the actual function!) that it couldn't be zero, but, unless I'm missing something, it's not as inevitable as you seem to imply.

Regards,

John

---------------------------------------------------------------- Dr John Whittington, Voice: +44 (0) 1296 730225 Mediscience Services Fax: +44 (0) 1296 738893 Twyford Manor, Twyford, E-mail: medisci@powernet.com Buckingham MK18 4EL, UK mediscience@compuserve.com ----------------------------------------------------------------


Back to: Top of message | Previous page | Main SAS-L page