I__. - International Military Testing Association

USING EVENT HISTORY TECHNIQUES TO ANALYZE TASK PERISHABILITY:
A SIMULATION
Spnley~ D. Stephenson
Southwest Texas State University
Julia A. Stephenson
University of North Texas
Until now, task perishability, the point in time at which a
~ task drops out of an airmanls inventory of tasks performed, has
not been researched. This lack of research could be for two reasons.
First, task performed/not performed is usually of more
interest than is when a task leaves a job inventory. Second,
perhaps measurement techniques for determining task perishability
are either unavailable or unknown. In any event, little is known
about task perishability. . _ .
For a variety of reasons, knowledge about task perishability
would be useful, primarily in training. For instance, the decision
about when and where to train a task (formal school or OJT)
could depend on how long the task is going to be used. Perhaps
the most obvious use of task perishability would be in crosstraining.
If a task can be determined to have a relative short
residual life, perhaps training on that task is not necessary,
even though the task is currently in the job inventory of comparable
time-in-grade airman. Also, task perishability is
obviously related to skill decay. A skill can be retained long
after a task stops being performed. However, if a task perishes
from an airman's inventory of tasks performed, the corresponding
skill will eventually leave that airman's inventory of skills.
Before skill decay can be measured, information about task perishability
should be known.
This paper will study the feasibility of measuring task perishability
using a technique called Event History Analysis.
There are two major features of event history as it applies to
task perishability. First, it incorporates time in the analysis;
;,zoAdhow long did a fa.sk stay in an airman's job inventory?
It has the ability to handle censored data. Censored
data i; data on which you have only partial information. For
example, not all airman complete their first term enlistment. Of
those who leave early, some will have stopped doing a task, but
some will still be performing the task. Consequently, information
about when the task would have left the censored airmen's
job inventories if they had stayed in the Air Force is unknown:
however, that the task lllivedll until the point of censoring is
known. Rather than discarding these censored data, event history
incorporates the available information and, although incomplete,
produces more precise estimates of task survivability.
TO study task perishability with event history techniques,
this paper used a simulated data base of a type which could be
derived from the data produced by the USAF Occupational Survey
Program and other sources.
USAF Occupational Survey Program
The USAF job analysis program is frequently referred to by
the term, CODAP (or TI/CODAP) (Christal & Weissmuller, 1988).
CODAP usually involves taking a snapshot of the entire work force
at one point in time; i.e., rather than being longitudinal, the
data collected is vertical. Consequently, the data do not provide
information about what an individual airman does over a 20
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