80% CI - T-value

Hi,

How to read t-value for a particular CI from a Table for parameter
estimates from regression. I want to know the t-value for 80% CI (am
using outputs from some other software - (HB-Reg) in which CI is set a
95%). So, I exported the output to SAS and want to perform the
t-calculations and reject less than 80% for various parameters. I knew
that t-value for 95% is +-1.96 critical range. So, I looked from a book
(John Freund's Mathematical Statistics, 6th edition) and in that the
value of 1.96 was there for DOF as infinity and alpha as .025. So I
thought that 0.025 relates to the 95% (I am not clear about one-tail, 2
-tail etc) and so for 80% CI I should probably consult the alpha value
= 0.1 and the DOF as infinity which came out to be 1.282. Am I correct
in this?

In tutorials (and SAS) the DOF for parameter estimates are give as one
(which I can appreciate as to why it is 1). But why is it that in above
case while reading of t-values from table one has to consult the row
where DOF is infinity?

Also, just for fun if I wanted to know how to find out the critical
value for let's say 70% CI then how should I go about it (in case I
dont have a table/book handy which already provides this value). Can I
generate the critical range numbers by putting in a formula in excel (I
know about excel not being suitable for Stats etc, but I just thought
as to probably it shouldnt make mistakes in generating these basic
values?) If its possbile to generate in Excel, please let me know the
method. This would probably help me in understanding the concept
better.

Regards,
Hari
India

.

Relevant Pages

  • Re: 80% CI - T-value
    ... I want to know the t-value for 80% CI (am ... > value of 1.96 was there for DOF as infinity and alpha as .025. ... > generate the critical range numbers by putting in a formula in excel (I ...
    (sci.stat.consult)
  • Re: 80% CI - T-value
    ... I want to know the t-value for 80% CI in which CI is set a 95%). ... So, I looked from a book and in that the value of 1.96 was there for DOF as infinity and alpha as .025. ... generate the critical range numbers by putting in a formula in excel (I ...
    (sci.stat.consult)
  • Re: When is text treated as number?
    ... When numbers are used in text expressions and functions, ... numbers should be treated as text; and indeed, that is what Excel ... instead Excel compares the internal representation of the objects ... the T-value for numbers. ...
    (microsoft.public.excel.misc)