Peter Baxter, DISTRIBUTIVE MANAGEMENT Hampton Roads INCOSE Decision Analysis Conference - Nov 2009 U SING M EASUREMENT AND THE S AATY M ETHOD TO C HOOSE.

Peter Baxter, DISTRIBUTIVE MANAGEMENT

Hampton Roads INCOSE Decision Analysis Conference - Nov 2009

USING MEASUREMENT AND THE SAATY METHOD TO CHOOSE THE BEST DECISION ALTERNATIVE

2 OBJECTIVES

Learn: How to construct and weight evaluation

criteria. How to make pair-wise comparisons of

alternatives. How to expand the example for more

complex, nested types of criteria. How a measurement process can support

the Saaty method.D I S T R I B U T I VE M A N A G E M E NT

WHAT IS THE AHP/SAATY METHOD?

4 SIMPLE DEFINITION

Compute the matrix values for a and … voila!

The Analytic Hierarchy Process (AHP)

D I S T R I B U T I VE M A N A G E M E NT

5

COMPARE THE SIZES

OF THESE CIRCLES

A B C D E

A B C D E

A 1 7 9 5 3

B 1/7 1 3 1/5 1/7

C 1/9 1/3 1 1/7 1/9

D 1/5 5 7 1 1/3

E 1/3 7 9 3 1D I S T R I B U T I VE M A N A G E M E NT

6SCALE OF

COMPARISON Don’t need an absolute scale

(if you already know the size of all but one)

Relative scale approximates difference


7SIMPLE

EXPERIMENT

One test is worth 1000 expert opinionsD I S T R I B U T I VE M A N A G E M E NT

8WEBER’S

EXPERIMENT

In 1846 Weber found, for example, that people while holding in their hand different weights, could distinguish between a weight of 20 g and a weight of 21 g, but could not if the second weight is only 20.5 g. On the other hand, while they could not distinguish between 40 g and 41 g, they could between 40 g and 42 g, and so on at higher levels. We need to increase a stimulus s by a minimum amount Δs to reach a point where our senses can first discriminate between s and s+Δs. Δs is called the just noticeable difference (jnd). The ratio r = Δs/s does not depend on s.

Weber’s law states that change in sensation is noticed when the stimulus is increased by a constant percentage of the stimulus itself. This law holds in ranges where Δs is small when compared with s, and hence in practice it fails to hold when s is either too small or too large.D I S T R I B U T I V

E M A N A G E M E NT

9 WHY IT WORKS

People are inconsistent at providing an absolute scale to evaluate objects.

How much does Rock A weigh?

How much does Rock B weigh?

There are better at comparing pairs of objects.

Does Rock A weigh more than Rock B?


10APPLYING THE

TECHNIQUE

1. Select criteria(s) to evaluate

2. Define comparison scale

3. Perform pair-wise comparison

4. Check consistency

5. Calculate values


APPLYING THE METHOD

12

EXAMPLE #1SOFTWARE

ESTIMATION A controlled test where existing software sizes are known.

Ask 30 grad students to estimate the SLOC of common data structures like stack, queue, list.

Estimate SLOC three ways:

1. Guess a number.

2. Compare to one reference structure using numeric scale.

3. Compare to one reference structure using relative scale.

Plot results

From “Establishing Software Size Using Pair-wise Comparison Method” by Eduardo Miranda


13EXAMPLE #1

SOFTWARE ESTIMATION


14EXAMPLE #1

OBSERVATIONS

Miranda’s Observations

The high variability of the “finger in the wind approach”, which is almost two to three times bigger than the corresponding paired comparisons method.

The high correlation, r = .979, existing between the relative sizes of modules independent of the estimation method employed. This seems to corroborate the premise that the human mind is better at establishing differences than at guessing absolute values.


15EXAMPLE #2

SYSTEM REQUIREMENTS

From an SEI study “Requirements Prioritization Case Study Using AHP” by Nancy Mead.

Given nine security requirements, decide which one(s) have greatest cost-benefit.

Benefits

“By using AHP, the requirements engineer can also confirm the consistency of the result. AHP can prevent subjective judgment errors and increase the

likelihood that the results are reliable.”


16EXAMPLE #2

APPROACH

Approach1. Review requirements for completeness.

2. Apply pair-wise comparison for value.

3. Apply pair-wise comparison for implementation cost.

4. Calculate AHP matrix and diagram for value & cost.

5. Use resulting diagram for analyzing requirements.


17EXAMPLE #2

COMPARISON SCALE


18EXAMPLE #2

COMPARISON

Compare one attribute of each requirement to another requirement using a relative scale.

#1 is same as #1

#1 is greater than #2

#2 is much less than #8


19ABOUT

CONSISTENCY

If: A > B > C

Then: C > A is wrong

AHP contains a technique to calculate the extent of pair-wise consistency, which can then be

compared to a consistency tolerance.

AHP can also indicate which pair-wise comparison (like the one above) is inconsistent.


20EXAMPLE #2

COMPARISON SUMMARY


21EXAMPLE #2

FINDINGS

Client feedback

It may be beneficial to see the consistency matrix.

Understand weight of cost and value.

Difficult to understand the motivation of each reviewer.


22 OTHER EXAMPLES

From Saaty:

Evaluate the best city in China for Disney to build a new theme park.

Determine optimum foreign relations policy for dealing with Iran.

Estimate market share of “super” retail stores.

Selecting a school. D I S T R I B U T I VE M A N A G E M E NT

MEASUREMENT AND AHP

24MEASUREMENT

AND AHPGoal is for Measurement to support AHP estimation

Estimate

Plan

Monitor & Control

Capitalize

Measurement Process

Use AHP


25

TYPICAL MEASUREMENT

PROCESS

Evaluate

EstablishCapability

Technical and Management

ProcessesINFORMATION NEEDS

ANALYSIS RESULTS

ANALYSIS RESULTS AND

PERFORMANCEMEASURESIMPROVEMENT

ACTIONS

Measurement Process

USER FEEDBACK

Plan Perform

Core Measurement Process

ExperienceBase

MEAS-UREMENTPLAN

26 WHAT TO MEASURE?

Measurement “Requirements” = information needs Based on your business needs.

(not a pre-defined list) Information needs are:

“Input” to the measurement process.

Provided by the management and technical process that need information to perform their jobs.

Become the requirements for measurement process.

Refined into measures and then resulting information products are provided to the “users”.


27COMMON PROJECT

MEASURES

Cost

Staffing , Staff Hours

Functional / Requirements Size

SLOC

Defects

Estimation Project/Program Store

Factors estimated using AHP


Usually there is opportunity for measurement to support AHP since there is overlap between what is estimated and what is measured

28MEASUREMENT

GUIDE AHP

Measurement contains project attributes:

Lifecycle model

Principle architecture

Application domain

AHP estimation of projects with similar attributes.

Reference sizes should not differ by more than an order of magnitude.


29 AHP IN USE

Estimate total staff hours in person years using data from five completed projects sharing similar attributes.


30 RESOURCES

“Requirements Prioritization Case Study Using AHP” by Nancy Mead Software Engineering Institute

“Establishing Software Size Using the Paired Comparisons Method” by Eduardo Miranda

“Relative Measurement and Its Generalization in Decision Making Why Pairwise Comparisons are Central in Mathematics for the Measurement of Intangible Factors The Analytic Hierarchy/Network Process” by Thomas Saaty


31 QUESTIONS


32

Peter Baxter

Distributive Management

www.distributive.com

[email protected]


mailto:[email protected]

mailto:[email protected]

Peter Baxter, DISTRIBUTIVE MANAGEMENT Hampton Roads INCOSE Decision Analysis Conference - Nov 2009 U SING M EASUREMENT AND THE S AATY M ETHOD TO C HOOSE.

Documents

values distributive

lternative slide

stimulus s

s izes

s imple e xperiment

w eber s e xperiment

s cale of c omparison

comparison scale