Human Reliability Flashcards
Definition of Human Reliability
Capacity of Humans to complete a task under given conditions within defined time and defined acceptance limits
Definition of Reliability Paramaters (theoretical, priori)
Characterizes the probability distributoin of a relability feature
Definition of Reliability Characteristics (empirical, posteriori
Characterize the Frequency distribution of a reliability feature
Definition of Availability Measure
Time in which the machine is available for work:
V = MTBF/(MTBF + MTTR)
MTBF = Mean time between Failures
MTTR = Mean time to Repair
Definition of Residual Risk
The Risk remaining after implementation of safety measures.
Passive vs Active Safety
Passive = Reducing the probability of damage after ocurrence of unwanted event (Seat belts)
Active = Reducing probability of an unwanted event happening (Autonomous Emergency Breaking)
Risk Equation
Risk = Probability x Severity
Human Error Probability Equation
HEP = N. of Errors Observed (n) / N. of Possibilities for an Error (N)
Binomial vs Poisson vs Weibull Distribution
Binomial = Finite number of samples
Poisson = Infinite Samples (Or very very large number of samples)
Weibull = Mostly useful to calculate lifespan, durability (Involves Time)
Calculating Probability with Binomial Distribution (Equation)
P(X = k) = (nk)(p)k(q)n-k
Where p = error probability
q = 1-p
Calculating Probability with Poisson Distribution
P(X = k) = ((n p)k/k!) e-np
where n x p is the expected value (µ) so:
P(X = k) = ((µ)k/k!) e-µ
Calculating Lifespan (failure) with Weibull Distribution
F(t) = 1 - e-(t/T)b
where T = time to which 63.2% of components have failed
b = shape parameter
F(t) = probability that the lifespan is at most equal to t
Survival Probability (Equation)
R(t) = 1- F(t)
1 - Failure probability at certain time
Bayes Theorem if Dependence is Assumed (equation):
P(A Ո B) = P(A|B)P(B) = P(B|A)P(A)
P(A|B) = P(B|A)P(A) / P(B)
P(A Ո B) = Probability that both A and B are True
Law of Total Probability (equation) P(B)
P(B) = P(B|A)P(A) + P(B|A-)P(A-)
Bayes Theorem (Equation)
P(A|B) = (P(B|A)P(A))/(P(B|A)P(A)+P(B|A-)P(A-))
Probability of A ocurring given that B is true
The probability of A and B being true is:
P(A and B) = P(A) x P(B)
Probability of A or B or both being true
P(A or B) = 1-[ (1-P(A)) x (1-P(B)) ]
Only applies if A and B are independent
Probability of either A or B (XOR)
P(A “or” B) = P(A) + P(B)
either A or B (NOT Both)
How is High Quality Ergonomics Achieved?
By:
-Use of a system-approach
-Design-based approach
-Equal performance in: performance and well-being.
What is the main approach for the analysis of human factors?
Organization, Machine, and Humans as separate entities but working with eachother.
Calculate Work Quality
Result/Task
Calculate work Performance
Work Quality/Time
What is “Working Task”?
What is requested to the operators. To do a task under given conditions and procedures to achieve a working result.
What is “Work Load”?
All external conditions/requirements in the working system that could influence a person.
What is “Working Stress”?
The effect of the Work Load on a person relative to his/her individual characteristics.
What is “Quality of Work”?
How much the working result matches the working task
What is the “Acceptance Area”?
Limits which define quality of work in accordance to requirements.