3

The book Software Metrics A Rigorous and Practical Approach defines measurement as

...the process by which numbers or symbols are assigned to attributes of entities in the real world in such a way so as to describe them according to clearly defined rules.

but what does it mean by "clearly defined rules"? Does this mean rules for assignment and comparison?

So, is “blue” a measure of the color of the room? Would "Bill" be a measure of the name of somebody? If not, why?

It then goes on to talk about the representational theory of measurement, defining measurement as a mapping from a domain to a range (Is this related to the earlier definition?):

...the mapping from the empirical world to the formal, relational world.

and that:

We can use real numbers, integers, or even a set of non-numeric symbols.

as the range. Note that it includes non-numeric symbols because then it says:

The representation condition asserts that a measurement mapping M must map entities into numbers...

Isn't this a contradiction?

Gary In
  • 133
  • 2
  • 1
    non-numeric symbols are used to represent ordinals, often expressed as adjectives. For instance, "very hard", "hard", "tough", "easy", "very easy", represents a range of hardness. Because they are ordinals, you can assign numbers to them in that order. You can work with those ordinals to calculate medians, averages, and even higher-order statistics. You may need to train your observers to agree on what the designations mean, but once they are trained, you have a repeatable set of observations that can be compared over time and over place. This is the essence of measurement. – BobDalgleish Nov 29 '16 at 21:51

1 Answers1

4

what does it mean by "clearly defined rules"?

It means rules that are clearly defined. For example, Source Lines of Code can be defined as physical lines of code (the number of lines separated by a carriage return), or the number of logical statements. Your assessment of the size of a program would depend greatly on which definition you use.

is “blue” a measure of the color of the room?

How many shades of blue do you know of?

It then goes on to talk about...

The point is that, if you define a measurement against a particular domain, someone else ought to be able to take your definition and come up with substantially the same objective measurement result as you did, given the same thing being measured, using whatever symbols you've chosen to define to make the measurement.

I say "substantially" because every measurement is subject to some margin of error, which should be a part of the measurement definition (i.e. everyone knows how accurate their slide rule is).

Robert Harvey
  • 198,589
  • 55
  • 464
  • 673