Functions and CALL Routines |
Returns a quantile from the chi-square distribution.
-
p
-
is a numeric probability.
Range: |
0 p
< 1 |
-
df
-
is a numeric degrees of freedom parameter.
-
nc
-
is a numeric noncentrality parameter.
Range: |
nc 0 |
The CINV function returns the pth quantile from the chi-square
distribution with degrees of freedom df and a
noncentrality parameter nc. The probability that
an observation from a chi-square distribution is less than or equal to the
returned quantile is p. This function accepts
a noninteger degrees of freedom parameter df.
If the optional parameter nc
is not specified or has the value 0, the quantile from the central chi-square
distribution is returned. The noncentrality parameter nc
is defined such that if X is a normal random variable with mean and variance 1, X2 has a noncentral
chi-square distribution with df=1 and nc = 2.
- CAUTION:
- For large values of nc,
the algorithm could
fail. In that case, a missing value is returned.
Note: CINV is the inverse of the PROBCHI
function.
The first statement following shows how to find the
95th percentile from a central chi-square distribution
with 3 degrees of freedom. The second statement shows how to find the 95th percentile from a noncentral chi-square distribution with
3.5 degrees of freedom and a noncentrality parameter equal to 4.5.
SAS Statements |
Results |
q1=cinv(.95,3);
|
7.8147279033
|
a2=cinv(.95,3.5,4.5);
|
7.504582117
|
Copyright © 2011 by SAS Institute Inc., Cary, NC, USA. All rights reserved.