Search All of the Math Forum:
Views expressed in these public forums are not endorsed by
NCTM or The Math Forum.


Math Forum
»
Discussions
»
sci.math.*
»
sci.stat.edu
Notice: We are no longer accepting new posts, but the forums will continue to be readable.
Topic:
Ftest for comparing variances?
Replies:
4
Last Post:
Nov 10, 2006 1:04 AM




Re: Ftest for comparing variances?
Posted:
Nov 8, 2006 11:01 PM


On 8 Nov 2006 11:08:22 0800, "Reef Fish" <large_nassua_grouper@yahoo.com> wrote:
> > Richard Ulrich wrote: > > On 5 Nov 2006 17:55:46 0800, "Reef Fish" > > <large_nassua_grouper@yahoo.com> wrote: > > > [snip]
RU > > > > umm. You still need to get a test value, subtract, then double.... > > which I described usefully. Bob was not paying attention, too eager > > to criticize. RF > > WRONG, WRONG, WRONG. > > 1. For testing with a given alpha, such as a twotailed test with F, > you find F(.025) and F(.975) before you get the test value, > because > you DON'T have to see if the numerator is greater or smaller. You > KNOW the degrees of freedom of the F.
I can apologize, and clarify.
No doubt I confused Bob by saying "test value" instead of saying "twotailed pvalue."
If you want a twotailed pvalue  which is the modern standard, instead of simply 'flagging' the test result  you need to double the smaller extreme.
Here are a *couple* of conventions  presenting pvalues; and doubling a onetailed value to get a twotailed value.
[snip]
RU > > > By now, he should recognize that he *often* does not understand > > what's being said. Why else is it, that every 'fight' in the stat > > groups features Bob? RF > > Everytime you say I don't understand, it's always because I was at > several steps AHEAD of you and understand every word of yours to > be ERRORS resulting from your lack of education.
Your next step, Bob, is to consider how to compute the "pvalue", which everyone wants these days. Catch up.
[snip] > > You REMAIN ignorant, and a malpracticing Quack, Richard Ulrich.
That remains absurd. Streamofconsciousness garbage.
> > That may be an insult you deserve  but hardly gratuitous!
Yes. Gratuitous. Nobody asks for this, and 10,000 readers do not want to see it. *If* I were so obviously 'ignorant', nobody would *need* Reef Fish Bob Ling to belabor the point.
The only 'end' that it seems to serve is an ongoing intention to bully and intimidate. Bad netcitizenship.
 Rich Ulrich, wpilib@pitt.edu http://www.pitt.edu/~wpilib/index.html



