(Joe) wrote in message . com...
What is students-t distribution [and why weren't we taught it in
class!]? How does it take into account the uncertainty of the
uncertainty? Does it take into account the uncertainty of that
uncertainty? How would you modify it to do so! As an aside, my
instructor says my error bars represent roughly [how ROUGH...] 2/3
"confidence level" of the true value (what ever that is). If you read
the error bars in my notebook as 90%, it would be misreading them.
And yet you specify 90% of something, what happens if I change it to
90.0000001%?

Student's t is a more advanced thing. Basically it widens the error
bars if the sample is small because the uncertainty is uncertain. It
takes the uncertainty of the uncertainty into account by assuming the
worst case.

2/3 is fine. 90% is fine too. Just draw the bars and make a note of
whatever confidence level you are using.

why weren't we taught it in
class!]?

You have to start somewhere. Start with general things, then go to
refinements.

And yet you specify 90% of something, what happens if I change it to
90.0000001%?

It makes the interval a tiny bit wider.