Question

18 , 20, 29, 31, 32,83

significant level = 0.02, to find A and B of qchisq ( A,B)? If critical value = 15, what is that mean?  

Answer 1

qchisq is a R software function to obtain quantile function of Chi square distribution.

qchisq(A, B) in R software will give us A^th percentile of Chi-square distribution with B degrees of freedom.

i.e. If we want 90th percentile of Chi-square distribution with 10 degrees of freedom then we will use qchisq(0.90, 10)

Critical value=15 is associated with Chi-square distribution with 5 degrees of freedom and significant level alpha=0.01

Since it's two sided test we take alpha/2 for lower tail and 1-alpha/2 for upper tail. Our given alpha is 0.02. So for upper tail (1-alpha/2) = 0.99 .

qchisq(0.99, 5) = 15 (approximately).

So critical value=15 means 99th percentile of Chi-square distribution with 5 degrees of freedom is 15 and corresponding R software function will be qchisq(0.99, 5) so A=0.99 and B=5.

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