Drexel dragonThe Math ForumDonate to the Math Forum



Search All of the Math Forum:

Views expressed in these public forums are not endorsed by Drexel University or The Math Forum.


Math Forum » Discussions » sci.math.* » sci.stat.math.independent

Topic: Why multiply t by sample std dev?
Replies: 7   Last Post: Oct 2, 2012 6:42 PM

Advanced Search

Back to Topic List Back to Topic List Jump to Tree View Jump to Tree View   Messages: [ Previous | Next ]
Bruce Weaver

Posts: 735
Registered: 12/18/04
Re: Why multiply t by sample std dev?
Posted: Oct 2, 2012 9:38 AM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

On 01/10/2012 9:54 PM, Rich Ulrich wrote:
> On Mon, 1 Oct 2012 12:45:45 -0700 (PDT), Paul
> <paul.domaskis@gmail.com> wrote:
>

>> On Sun, 30 Sep 2012 12:55:11 -0700 (PDT), Paul
>> <paul.domas...@gmail.com> wrote:

>
> ... snip a bunch
>

>> Thanks, Dave, Rich,
>>
>> I think I pin-pointed the source of my confusion. I didn't really
>> know what t was. It was just a curve and a table that we blindly used
>> according to a recipe. Well, Wikipedia

> (http://en.wikipedia.org/wiki/Student%27s_t-distribution) defined the
> t-value in a manner similar to

>> Rich:
>>
>> [ (sample mean) - (population mean) ] / (sample standard deviation)
>>

>
> No!
> It does not say that. It uses the sample standard ERROR.
> You are going to confuse yourself on into the future if you do
> not grasp the distinction and keep it clear.
>
> The Standard Error is the name used for the SD of a statistic.
> Yes, it is also a standard deviation. But the "SD of a sample"
> is distinct and larger than the "SD of a sample mean."



And to complete the thought, the (estimated) standard error (SE) of the
MEAN = the sample SD divided by the square root of the sample size.


--
Bruce Weaver
bweaver@lakeheadu.ca
http://sites.google.com/a/lakeheadu.ca/bweaver/Home
"When all else fails, RTFM."



Point your RSS reader here for a feed of the latest messages in this topic.

[Privacy Policy] [Terms of Use]

© Drexel University 1994-2014. All Rights Reserved.
The Math Forum is a research and educational enterprise of the Drexel University School of Education.