4.2 Measurement Issues In Ordering And Evaluating Objectives

Question 1

What are crucial characteristics of a ruler or scale in engineering?

Answer 1

In engineering, a ruler or scale must have:

• A defined Zero
• Units that define the markings scribed onto the ruler

Question 2

The following properties of a ruler or scale important in engineering, because they enable what types of measurements?

• A defined Zero
• Units that define the markings scribed onto the ruler

Answer 2

A defined zero and units (that define the markings scribed onto the ruler) enable strong measurements.

Question 3

Why are strong measurements desirable?

Answer 3

Strong measurements:

• Allow us to treat measured mathematical variables (say L for length, T for temperature, and so on)
• Can be used as any of our “normal” physical variables in a mathematical model

Question 4

What scale is normally used to measure things against each other?

Answer 4

We generally use ordinal scales to place things in rank order, i.e. first, second, or nth place.

Examples:

In a race at the finish line, without a watch: We can tell the order of the racers’ arrivals, but not their respective times. Thus, we can say that A is faster than B, who is faster than C, and so on- but we can never say by how much.

Similarly, people say that they prefer vanilla ice cream to chocolate, but not by how much.

Question 5

What is the problem associated with asking a client to set priorities?

Answer 5

The problem associated with asking the client to set priorities is we are really asking for a subjective ranking of their relative importance.

Example:

The client may prefer portability over price in designing a new laptop computer, but there is no meaningful way to say that “portability is five times more important than cost” because there is ·no scale or ruler that defines both a zero and a unit with which to make such measurements.