Question

On this, at 3:24, he talks about program inverse chi-square distribution. Does anyone know about it? Please post the code or give me the link.
Thanks in advance
https://www.youtube.com/watch?v=nFieXUy9Rxs

Answer 1

@myininaya

Answer 2

try

solve(\(\chi^2\)cdf(0,\(x\),n)-(1-\(\alpha\)),\(x\),n)

where \(n\) is the degrees of freedom and \(\alpha\) is the number such that \[P(X\ge \chi^2_{n})=\alpha\]

Answer 3

Suppose I need find \(P(a< X_4^2<b)=0.90\), how to hit the keys on my ti83?

Answer 4

you trying to find the confidence interval?

Answer 5

That is the last step and I can find it by hand.

Answer 6

in general a and b are not unique

Answer 7

Yes, I know. Suppose we choose \(P( X_4^2 <a) =0.05\) then how to find a?

Answer 8

\[\text{solve}(\chi^2cdf(0,x,4)-.05,x,4)\]

Answer 9

then

\[\text{solve}(\chi^2cdf(0,x,4)-.95),x,4)\] for b

Answer 10

It does not work. Do you mean \(X^2cdf(0,x,4) - X^2 cdf(0.05,x,4)\)?

Answer 11

works on mine

Answer 12

ah...jas

Answer 13

\[\text{solve}(\chi^2cdf(0,x,4)-.05,x,4)\]
\[\text{solve}(\chi^2cdf(0,x,4)-.95,x,4)\]

Answer 14

had an extra parenthesis

Answer 15

solve (.....)
I don't have that word on my calculator. :)

Answer 16

you do...

look in the catalog

Answer 17

2nd 0

Answer 18

YYYYYYYYYYYes. Thanks a ton....

Answer 19

vid

Answer 20

happy you got it

Answer 21

woah... You should teach your students this method. It save a lot of lives. :)

Answer 22

i wrote a program to find the CI on the 83/84 and I share it with my students

Answer 23

Best Professor ever. :)

Answer 24

sure ;)

Answer 25

I am greedy :) but I would like to have that program too. :)
Please.

Answer 26

all you need to do :

have inputs \(s^2\),d.f.(D) and Confidence level (C)

then compute

\[\chi^2_{L}=\text{solve}(\chi^2cdf(0,x,D)-(1-C)/2,x,D)\]

\[\chi^2_{R}=\text{solve}(\chi^2cdf(0,x,D)-(1+C)/2,x,D)\]

C.I for \(\sigma^2\)is given by

\[\left[\frac{D s^2}{\chi^2_{R}},\frac{D s^2}{\chi^2_{L}}\right]\]

Answer 27

I need a concrete example to understand it.
Example 8.7 text book, how to use this code ?

Answer 28

example 8.7 doesn't use a chi square

it uses a z-interval...that is built in to your ti 83