From Page 15
(3) You are correct.
It occurs to us that at this point in your
training, the most
effective learning (or refresher) tactic might be to
present a checklist
that summarizes some of the key concepts and rules of
thumb to follow when
dealing with control design.
So, we did just that
and put it in your
supplement for Lesson 40.
Okay, we've made it through the first 20 lessons; now, it's time to
move on to the next 20 lessons and deal with how the human fits into the
system. Let's begin by dealing with a number of factors that are important
aspects of any system; for example, system maintainability, which involves
designing for effective and efficient maintenance.
In this lesson, we
discussed an important concept known as operational availability which
represents the quantitative description of how often the system is working.
Can you remember two key measures of operational availability?
What are
these measures and to what do they relate?
You remember that MTTR (Mean Time To Repair) is a measure of
maintainability and MTBF (Mean Time Between Failures) is a measure of
reliability.
We bet you also remember that MTBF typically does not take
into account human performance reliability, but only system reliability.
You learned that to attend to the reliability of the hardware only results
in solving only 50 percent of the total reliability problem.
You also
learned that human performance reliability information can be used to derive
two measures of complexity. What are these two measures?
(1) Human limitations and capabilities. Turn to Page 93.
(2) Configuration and machine complexity. Turn to Page 78.
(3) Task and hardware complexity. Turn to Page 3.
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