The routine may be called by the names g01eaf or nagf_stat_prob_normal.
The lower tail probability for the standard Normal distribution,
is defined by:
is used, where erfc is the complementary error function, and is computed using s15adf. For the upper tail probability the relationship is used and for the two tail significance level probability twice the probability obtained from the absolute value of is returned.
When the two tail confidence probability is required the relationship
is used, where erf is the error function, and is computed using s15aef.
Hastings N A J and Peacock J B (1975) Statistical Distributions Butterworth
1: – Character(1)Input
On entry: indicates which tail the returned probability should represent.
The lower tail probability is returned, i.e., .
The upper tail probability is returned, i.e., .
The two tail (significance level) probability is returned, i.e., .
The two tail (confidence interval) probability is returned, i.e., .
, , or .
2: – Real (Kind=nag_wp)Input
On entry: , the value of the standard Normal variate.
3: – IntegerInput/Output
On entry: ifail must be set to , or to set behaviour on detection of an error; these values have no effect when no error is detected.
A value of causes the printing of an error message and program execution will be halted; otherwise program execution continues. A value of means that an error message is printed while a value of means that it is not.
If halting is not appropriate, the value or is recommended. If message printing is undesirable, then the value is recommended. Otherwise, the value is recommended. When the value or is used it is essential to test the value of ifail on exit.
On exit: unless the routine detects an error or a warning has been flagged (see Section 6).
6Error Indicators and Warnings
If on entry or , explanatory error messages are output on the current error message unit (as defined by x04aaf).
Errors or warnings detected by the routine:
If , then g01eaf returns .
On entry, .
Constraint: , , or .
An unexpected error has been triggered by this routine. Please
See Section 7 in the Introduction to the NAG Library FL Interface for further information.
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.
Dynamic memory allocation failed.
See Section 9 in the Introduction to the NAG Library FL Interface for further information.
Accuracy is limited by machine precision. For detailed error analysis see
8Parallelism and Performance
Background information to multithreading can be found in the Multithreading documentation.
g01eaf is not threaded in any implementation.
Four values of tail and x are input and the probabilities calculated and printed.