HAZARD
Name:
Type:
Purpose:
Compute the hazard for a set of failure times.
Description:
The hazard is constructed as follows:
 Sort and rank the N failure times from shortest
to longest failure time. Note that the hazard can
accomodate data where the time may be a censoring
time rather than a failure time (i.e., the unit was
taken out of service before it failed).
 Calculate a hazard value at each of the failure
times. Note that the hazard is only caclulated at
failure times, not censoring times. The hazard is:
where K is the rank of the failure time. This
expresses the hazard as a percentage. You can
express the hazard as a proportion by omitting
the multiplication by 100.
Syntax:
LET <y> = HAZARD <x> <tag>
<SUBSET/EXCEPT/FOR qualification>
where <x> is the variable containing the failure times;
<tag> is a variable that indicates whether the
corresponding element of <x> is a failure
time or a censoring time;
<y> is a variable where the hazards are saved;
and where the <SUBSET/EXCEPT/FOR qualification> is optional.
A value of 0 for <tag> is used to signify a
censoring time and a value of 1 for <tag> is used
to signify a failure time. Dataplot uses 0.5 as the
cutoff. That is, any value greater than or equal to 0.5
is interpreted as a failure time.
Examples:
LET Y = HAZARD X CENSOR
LET Y = HAZARD X CENSOR SUBSET CENSOR = 1
Note:
Hazards are only computed for failure times (i.e., where
= 1), not censoring times. The saved hazards ()
are set to 0 for censoring times. If you just want to keep
the hazards at failure times, do something like:
LET Y = HAZARD X CENSOR
RETAIN Y SUBSET CENSOR = 1
The censoring times do affect the value of the hazard since
they are used in determining the rank. If you only want the
failure times to be used in the calculation of the hazard,
do something like the following:
LET Y = HAZARD X CENSOR SUBSET CENSOR = 1
RETAIN Y SUBSET CENSOR = 1
Default:
Synonyms:
Related Commands:
CUMULATIVE HAZARD

= Compute the cumulative hazard for a variable.

HAZARD PLOT

= Generate a hazard plot.

PROBABILITY PLOT

= Generate a probability plot.

WEIBULL PLOT

= Generate a Weibull plot.

INTERARRIVAL TIME

= Compute the interarrival times of a variable.

Applications:
Implementation Date:
Program:
SKIP 25
READ HAHN.DAT Y TAG
LET TAG = 0 SUBSET TAG = 2
LET Z = HAZARD Y TAG
Date created: 6/5/2001
Last updated: 4/4/2003
Please email comments on this WWW page to
alan.heckert@nist.gov.
