NAG FL Interface
g08clf (gofstat_​anddar_​exp)

1 Purpose

g08clf calculates the Anderson–Darling goodness-of-fit test statistic and its probability for the case of an unspecified exponential distribution.

2 Specification

Fortran Interface
Subroutine g08clf ( n, issort, y, ybar, a2, aa2, p, ifail)
Integer, Intent (In) :: n
Integer, Intent (Inout) :: ifail
Real (Kind=nag_wp), Intent (In) :: y(n)
Real (Kind=nag_wp), Intent (Out) :: ybar, a2, aa2, p
Logical, Intent (In) :: issort
C Header Interface
#include <nag.h>
void  g08clf_ (const Integer *n, const logical *issort, const double y[], double *ybar, double *a2, double *aa2, double *p, Integer *ifail)
The routine may be called by the names g08clf or nagf_nonpar_gofstat_anddar_exp.

3 Description

Calculates the Anderson–Darling test statistic A2 (see g08chf) and its upper tail probability for the small sample correction:
Adjusted ​ A2 = A2 1+0.6/n ,  
for n observations.

4 References

Anderson T W and Darling D A (1952) Asymptotic theory of certain ‘goodness-of-fit’ criteria based on stochastic processes Annals of Mathematical Statistics 23 193–212
Stephens M A and D'Agostino R B (1986) Goodness-of-Fit Techniques Marcel Dekker, New York

5 Arguments

1: n Integer Input
On entry: n, the number of observations.
Constraint: n>1.
2: issort Logical Input
On entry: set issort=.TRUE. if the observations are sorted in ascending order; otherwise the routine will sort the observations.
3: yn Real (Kind=nag_wp) array Input
On entry: yi, for i=1,2,,n, the n observations.
Constraint: if issort=.TRUE., values must be sorted in ascending order. Each yi must be greater than zero.
4: ybar Real (Kind=nag_wp) Output
On exit: the maximum likelihood estimate of mean.
5: a2 Real (Kind=nag_wp) Output
On exit: A2, the Anderson–Darling test statistic.
6: aa2 Real (Kind=nag_wp) Output
On exit: the adjusted A2.
7: p Real (Kind=nag_wp) Output
On exit: p, the upper tail probability for the adjusted A2.
8: ifail Integer Input/Output
On entry: ifail must be set to 0, -1 or 1. If you are unfamiliar with this argument you should refer to Section 4 in the Introduction to the NAG Library FL Interface for details.
For environments where it might be inappropriate to halt program execution when an error is detected, the value -1 or 1 is recommended. If the output of error messages is undesirable, then the value 1 is recommended. Otherwise, if you are not familiar with this argument, the recommended value is 0. When the value -1 or 1 is used it is essential to test the value of ifail on exit.
On exit: ifail=0 unless the routine detects an error or a warning has been flagged (see Section 6).

6 Error Indicators and Warnings

If on entry ifail=0 or -1, explanatory error messages are output on the current error message unit (as defined by x04aaf).
Errors or warnings detected by the routine:
ifail=1
On entry, n=value.
Constraint: n>1.
ifail=3
issort=.TRUE. and the data in y is not sorted in ascending order.
ifail=9
The data in y must be greater than zero.
ifail=-99
An unexpected error has been triggered by this routine. Please contact NAG.
See Section 7 in the Introduction to the NAG Library FL Interface for further information.
ifail=-399
Your licence key may have expired or may not have been installed correctly.
See Section 8 in the Introduction to the NAG Library FL Interface for further information.
ifail=-999
Dynamic memory allocation failed.
See Section 9 in the Introduction to the NAG Library FL Interface for further information.

7 Accuracy

Probabilities are calculated using piecewise polynomial approximations to values estimated by simulation.

8 Parallelism and Performance

g08clf is threaded by NAG for parallel execution in multithreaded implementations of the NAG Library.
Please consult the X06 Chapter Introduction for information on how to control and interrogate the OpenMP environment used within this routine. Please also consult the Users' Note for your implementation for any additional implementation-specific information.

9 Further Comments

None.

10 Example

This example calculates the A2 statistics for data assumed to arise from an unspecified exponential distribution and calculates the p-value.

10.1 Program Text

Program Text (g08clfe.f90)

10.2 Program Data

Program Data (g08clfe.d)

10.3 Program Results

Program Results (g08clfe.r)