t distribution

[math magic]

Hi
I'm wondering if anyone can help me with t distribtuion questions. I don't know how to solve the questions below. If anyone can help it would be greatly appreciated. Thanks.

Find t such that P(T>t)=0.9 with 23 df
Find t such that P(T<t)=0.25 with 19 df
Find the prob P(T>2.6) with 15 df
Find the prob P(<-1.4) with 24 df

[eranga262154]

First of all you need a t-distribution table.

Then, for P(T>t)=0.9 with 23 df, find df(degree of freedom) 23 first and then find the given probability, 0.9. Most of the time you wont come up eith the exact probability. You have to do the interpolation to get the result.

When comes to the P(T<t)=0.25 with 19 df, first find the result and after get to the (1 - result) for the P(T<t).

To find the probability you have do it in other way around.

[eranga262154]

Here is a link for that kind of statics.

http://www.stat.tamu.edu/stat30x/zttables.html

[math magic]

Thanks for replying eranga262154. I think I understand it but can you please check my results to see if I'm doing it right as I'd wouldn't like to think I know how to do it but it isn't right.
The answers I got were:
Find t such that P(T>t)=0.9 with 23 df
t= 1.319
Find t such that P(T<t)=0.25 with 19 df
t=0.688
Find the prob P(T>2.6) with 15 df
P=0.01
Find the prob P(<-1.4) with 24 df
P=0.1

[eranga262154]

100% correct.

Make sure that interpolation will cause the loose of precisions.