chi sqaure & confidence interval

sstudent

Lets say you have 5 trials, and 5 output lets say {5, 43, 60, 30 , 4}....so how would u get the chi sqaure from here & the confidence interval. i havent work on prob &statc in years, thanks a lot for help folks

konthelion

I'm supposing you made up this problem... for your random sample of size n=5 is {5, 43, 60, 30 , 4},these are your observed cells/frequencies, but you do not have have your expected cells/frequencies.

sstudent

Basically u can do the confidence for 99%

konthelion

I don't understand what you're trying to do.

For a Chi-Squared test, you need a null hypothesis and alternative hypothesis.
The test statistical value is [tex]\chi^2=\sum \frac{(O-E)^2}{E} [/tex]
where O is a shorthand notation for your observed cells and E is the shorthand notation for expected cell/frequency.

If you are trying to find the confidence interval for the true variance [tex]\sigma^2[/tex], then the formula for that is

[tex] P\left( C_{1}< \frac{(n-1)s^2}{\sigma^2} < C_{2} \right) = 1- \alpha[/tex] = .99 since 100(1-alpha)% =99%

where [tex]C_{1}=\frac{(n-1)s^2}{\chi_{\alpha/2,n-1}}[/tex] is the lower limit
and
[tex]C_2 = \frac{(n-1)s^2}{\chi_{1-\alpha/2,n-1}}[/tex] is your upper limit.

sstudent

lets say u consider #5 as the thresh#, and for the numbers> 5, u tryto find the confiendnce interval for 99.99% or greater. thanks