Software Cost Estimation

Question 1

Software Cost Estimation

Answer 1

Involves predicting the resources required for a software development process.

Question 2

Fundamental Estimation Questions

Answer 2

• How much effort is required to complete an activity?
• How much calendar time is needed to complete an activity?
• What is the total cost of an activity?
• Project estimation and scheduling and interleaved management activities.

Question 3

Software Cost Components

Answer 3

• Hardware and software costs.
• Travel and training costs.
• Effort costs (salaries of engineers, social and insurance cost)
• Effort costs must take overheads into account (building, lighting, heating, networking, communications, shared facilities)

Question 4

Cost and Pricing

Answer 4

Estimates are made to discover of producing a software system.

Question 5

Software Pricing Factors

Answer 5

• market opportunity
• cost estimate uncertainty
• contractual terms
• requirements volatility
• financial health

Question 6

Programmer Productivity

Answer 6

A measure of the rate at which individual engineers involved in software development produce software and associated documentation.
We want to measure useful functionality produced per time unit.

Question 7

Productivity Measures (Size-Related measures)

Answer 7

Based on some output from the software process.

Question 8

Productivity Measures (Function-related measures)

Answer 8

Based on an estimate of the functionality of the delivered software.

Question 9

Estimation Problems (for productivity)

Answer 9

• Estimating size of the measure.
• Estimating the total number of programmer months which have elapsed.
• Estimating contractor productivity and incorporating this estimate in overall estimate.

Question 10

Productivity Comparisons

Answer 10

The lower level the language, the more productive the programmer.

Question 11

Function Points

Answer 11

Based on combination of program characteristics:
- External inputs and outputs.
- User interactions.
- External interfaces.
- Files used by the system.
A weight is associated with each of these.

Question 12

Object Points

Answer 12

Alternative function-related measure to function points.
Object points != object classes.
Number of object points in a program is a weighted estimate of:
- Number of separate screens that are displayed.
- Number of reports that are produced by the system.
- Number of modules that must be developed.

Question 13

Factors Affecting Productivity

Answer 13

• application domain experience
• process quality
• project size
• technology support
• working environment

Question 14

Quality and Producitivity

Answer 14

Metrics can be based on volume/unit time.
Productivity may be increased as the cost of quality.

Question 15

Estimation Techniques

Answer 15

There is no simple way to make an accurate estimate of the effort required to develop a software system (initial estimates are based upon inadequate information, unfamiliar computers, unknown amount of people in project).

Question 16

Self-fulfilling Product Cost

Answer 16

The estimate defines the budget and the product is adjusted to meet the budget.

Question 17

Estimation Techniques

Answer 17

• Algorithmic cost modelling.
• Expert judgement.
• Estimation by analogy.
• Parkinson’s Law.
• Pricing to win.

Question 18

Algorithmic Code Modelling

Answer 18

A formulaic approach based on historical cost information and which is generally based on size of software.
Formula - A x (Size^B) X M
A = Organisation-dependent constant
B = disproportionate effort for large projects
M = multiplier reflecting product, process and people attributes.

Question 19

Expert Judgement

Answer 19

One or more experts in both software development and the application domain use their experience to product software costs.

Question 20

Expert Judgement Advantages and Disadvantages

Answer 20

Adv: cheap estimation method and can be accurate.
Dis: very inaccurate is there are no experts.

Question 21

Estimation By Analogy

Answer 21

Cost of project is computed by comparing the project to a similar project in the same application domain.

Question 22

Estimation By Analogy Advantages and Disadvantages

Answer 22

Adv: accurate if project data available.
Dis: impossible if no comparable project gas been tackled.

Question 23

Parkinson’s Law

Answer 23

The project costs whatever resources are available.
Adv: no overspend.
Dis: system is usually unfinished.

Question 24

Parkinson’s Law Advantages and Disadvantages

Answer 24

Adv: no overspend.
Dis: system is usually unfinished.

Question 25

Pricing To Win

Answer 25

The project costs whatever the customer has to spend on it.
Pricing to win seems unethical and unbusinesslike, but when detailed information is lacking it may be the only appropriate strategy.

Question 26

Pricing To Win Advantages and Disadvantages

Answer 26

Adv: you get the contract.
Dis: the probability of the customer getting the system they want is small, because costs do not accurately reflect work required.

Question 27

Top-Down Estimation

Answer 27

Start at system level and assess overall system functionality and how this is delivered through subsystems.

Question 28

Bottom-Up Estimation

Answer 28

Start as component level and estimate effort required for each component. Add these efforts to reach final estimate.

Question 29

Experienced-based Estimations

Answer 29

Estimating is mainly based upon experience, however, new methods and technologies may make estimating based on experience inaccurate.

Question 30

Estimation Accuracy

Answer 30

Size of software system can only be known when finished.
Several factors influence the size:
- Use of COTS and components.
- Programming language.
- Distribution of system.
Size becomes more accurate when development progresses.