# find probability of chi2 test

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Mustafa Al-Nasser on 16 Mar 2021
Dear all;
if i want to perfrom a hypothesis test for chi2 distrubtion , how can i do it in matlab :
P(X>a)= alpha
Mustafa Al-Nasser on 21 Mar 2021
thank you Asvin
basically i need to test the following hypothesis
P(X> Chi2_Cirtical value)= alpha
Chi2_Cirtical value calcuated from central Chi2 distribution table , alpha is the signifacnce level
so, i need to check if the hypothesis hold if the above equatio is satisifed .
let us assume that Chi2_Cirtical value= 5.99 at alpha= 0.05 .at degree of freedom 2
in chi2gof. , i can specify the alpha but to specify the Chi2_Cirtical value , I need to know the degree of freedom.
if i use above function , i can got degree of freedeom , so since i know alpha i, i can check if the dgree of freedom > 2 , then X> 5.99 and my ypothesis is hold.
Is my conclusion is right?
Asvin Kumar on 21 Mar 2021
Thanks for explaining. I'm, unfortunately, not the right person for this question. I was merely suggesting a function I had come across in the docs. I'll let someone else from the community help you with this.

Ive J on 21 Mar 2021
Based on what you explained it seems you already have the X2 stat.
p = 1 - chi2cdf(x, nu) % where x is chi2 stat and nu is df

Aditya Patil on 29 Mar 2021
To elaborate on @Ive J's answer,
You have X. using chi2cdf, you can get . So in your case, , which you can get using chi2cdf as follows
p = 1 - chi2cdf(X, a)