BigAlOz

11-14-2013, 08:38 PM

I am trying to work out how to use the gammadist to calculate the Chi-Squared probability.

Basically I have

1. A Least squares adjustment

2. I have the degrees of freedom (measurements - unknowns)

3. The adjustmnet calculates the variance factor (VF)

4. Need to do Chi squared test on the Variance factor

- Test that the VF is statistically within the expected probability

- Test the VF againt unity at the 95% probability

I tried this

Gammadist gm(m-u,0.5)

// m-u = degrees of freedom

// 0.5 used as the text suggested this

x = gm.p(VF)

// i am assuming this should be a number between 0 and 1

// *100 = %

y = gm.cdf(VF)

// don't know what this might mean

Anyway I don't get reasonable values using the above.

Could somebody please explain how this function should be called.

Thanks in Advance

Alan

Basically I have

1. A Least squares adjustment

2. I have the degrees of freedom (measurements - unknowns)

3. The adjustmnet calculates the variance factor (VF)

4. Need to do Chi squared test on the Variance factor

- Test that the VF is statistically within the expected probability

- Test the VF againt unity at the 95% probability

I tried this

Gammadist gm(m-u,0.5)

// m-u = degrees of freedom

// 0.5 used as the text suggested this

x = gm.p(VF)

// i am assuming this should be a number between 0 and 1

// *100 = %

y = gm.cdf(VF)

// don't know what this might mean

Anyway I don't get reasonable values using the above.

Could somebody please explain how this function should be called.

Thanks in Advance

Alan