ENGR101 – Engineering
Engineers Make Decisions
How to make decisions
The Wikipedia way?
Some of the decision making techniques people use in
everyday life include:
• Satisficing: Accepting the first option that seems like it
might achieve the desired result
• Acquiesce to a person in authority or an "expert", just
• Flipism: Flipping a coin, cutting a deck of playing
cards, and other random or coincidence methods
• Prayer, tarot cards, astrology, augurs, revelation, or
other forms of divination
How to make decisions
The Engineering way?
Engineers analyse problems in order to make decisions:
• Synthesis: combine the important elements into an
• Analysis: using Mathematics, Science, Engineering
techniques and others (e.g. Economics) to quantify the
performance of various options.
• Communication: described the decision and how/why
it was made.
• Implementation: engineers execute the consequences
Mathematics, especially statistics, are a useful tool in
understanding the likelihood of success.
Given a set of numbers:
• Mean: the average
• Median: middle of the sorted set
• Mode: most frequent
Standard deviation: square root of variance
• Expected value E X (ave.)
• Standard deviation
Mathematics, like any tool, must be used properly.
Student’s T-Test to defeat the null hypothesis.
[There is no difference in the decisions to be made]
Confidence in Decisions ...
Guess versus Estimate
Guess: pulled out of thin air
“Yes, I am certain that this will work”
Estimate: prediction of the future based on past results,
research, analysis, engineering ...
“I am 90% confident based on these calculations, and
prior testing, that this may work”
Pros vs Cons
Straightforward decision-making approach
List all the features of the problem/solutions
Determine the strengths and weaknesses.
Criteria are used to quantify solutions
• pass/fail or
• rank based or
• numerical or ...
• Soft constraint (flexible to not meet criterion)
• Hard constraint (must meet criterion)
Single vs Multiple
• Single criterion: easy to judge, but rare in real life
• Multiple criteria: trade-offs and compromises
1. Weight each criteria
2. Score each option
3. Sum up totals
4. (adjust weights, so favoured solution wins)
Weight Option 1 Option 2 ...
W S SxW S SxW
Cost 5 3 15 4 20
Speed 3 2 6 3 9
Lift 3 4 12 3 9
... ... ... ... ... ...
Total 50 45
1. Trade-offs between different solutions
e.g. Wish to minimise the number of robot collisions (f1)
and cost (f2)
Easy to do,
No guarantees. lucidry.org
Rhino in the Road
Left is good
Right is good
Go in the middle!
As little as possible...
Head vs Heart
Or more precisely:
Anterior cingulate cortex, orbitofrontal cortex, ventromedial
Amygdala, Hippocampus, Hypothalamus.
New ‘rational’ brain Vs Old ‘emotional’ brain
‘people who spend too much time analysing their options are
less satisfied with their decisions’
Lehrer, “The Decisive Moment”.
"They who dream by day are cognizant of many things which
escape those who dream only by night." (Edgar Allen Poe)
Find decision-making methods that work for you.
If you don't like the answer that the decision-making
sheet(s) reflect back to you...
it means you haven't included all the cons
- especially the emotional ones –
or you haven't scored the factors consistently,
so re-visit the sheet(s) concerned.