Hoofdstuk 10 - Metrics

Question 1

Can you give three possible problems of metrics usage in software engineering? How does the measurement theory address them?

Answer 1

◦ Preciseness: Do we use the same units to compare?
◦ Representation Condition: Is “code size” really what we want to have?
◦ Scale and Scale Types: How do we want to interpret results?
◦ GQM-paradigm: What do we want to do with the results?
◦ The measurement theory helps to answer the questions by providing good techniques.

Question 2

What’s the distinction between a measure and a metric?

Answer 2

◦ A measurement is a function mapping of an attribute of a real world entity onto a symbol in a set of known mathematical relations
◦ A metric is a measurement with as range the real numbers and which satisfies m(x,x)=0, m(x,y)=m(y,x) and m(x,z)<m(x,y)+m(y,z)

Question 3

Can you give an example of a direct and an indirect measure?

Answer 3

◦ Direct: lines of code
◦ Indirect: module defect density

Question 4

What kind of measurement scale would you need to say “A specification error is worse than a design error”? And what if we want to say “A specification error is twice as bad as a design error?”

Answer 4

For the first ordinal, for the second ratio

Question 5

Explain the need for a calibration factor in Putnam’s model.

Answer 5

◦ The calibration factor is needed because projects and teams have different sizes.
◦ To know the parameters that influence the effort

Question 6

Fill in the blanks in the following sentence. Explain briefly, based on the Putnam’s model.
+ If you want to finish earlier (= decrease scheduled time), you should … the effort … .

Answer 6

If you want to finish earlier, you should increase the effort a lot

Question 7

Give three metrics for measuring size of a software product.

Answer 7

◦ Lines of Code
◦ Function Points
◦ Use Case Points.

Question 8

Discuss the main advantages and disadvantages of Function Points.

Answer 8

◦ :) measured after the design,
independent of implementation language,
measures functionality and works well for data-processing.

◦ :( It requires subjective expert judgment
and cannot be calculated automatically.

Question 9

What does it mean for a coupling metric not to satisfy the representation condition?

Answer 9

It means that coupling might not be representable enough to be a sufficient metric.

Question 10

Can you give 3 examples of impreciseness in Lines of Code measurements?

Answer 10

◦ Ignores software reuse, code duplication, benefits of redesign.
◦ The lower level the language, the more productive the programmer.
◦ The more verbose the programmer, the higher the productivity.