Decision Methods

8/11/2019 Decision Methods

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DECISION METHODS FOR EVALUATION

OF ALTERNATIVES

Environmental impact studies typically address a minimum of

two alternatives, and sometimes as many as ten, but usually

three to five alternatives

Typical categories of alternatives, expressed generically,

include

Site location alternatives

Design alternatives for a site

Construction, operation, and decommissioning alternatives for a

design Project size alternatives

Phasing alternatives for size groupings

No-project or no-action alternatives

Timing alternatives relative to project construction, operation,and

decommissioning


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Conceptual Basis for Tradeoff

Analysis Tradeoff analysis involves the comparison of a set of alternatives

relative to a series of decision factors.

The following approaches can be used to complete the tradeoffmatrix

Qualitative approach: Descriptive, synthesized, and integrated

information on each alternative relative to each decision factoris presented in the matrix.

Quantitative approach: Quantitative, synthesized, andintegrated information on each alternative relative to eachdecision factor is displayed in the matrix.

Ranking, rating, or scaling approach: The qualitative orquantitative information on each alternative is summarized viathe assignment of a rank, rating, or scale value relative to eachdecision factor (the rank or rating or scale value is presented inthe matrix).


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Weighting approach: The importance weight of eachdecision factor relative to each other decision factor

is considered, with the resultant discussion of theinformation on each alternative (qualitative;quantitative; or ranking, rating, or scaling) beingpresented in view of the relative importance of thedecision factors.

Weighting-ranking, -rating, or -scaling approach:The importance weight for each decision factor ismultiplied by the ranking, rating, or scaling of eachalternative, then the resulting products for each

alternative are summed to develop an overallcomposite index or score for each alternative; theindex may take the form of:

Index j = (IW)i (R)ij


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TRADEOFF ANALYSIS FOR DECISION MAKING (CANTER,ATKINSON, AND LEISTRITZ 1985)

Alternatives

Decision Factors 1 2 3 4 5

Degree of Meeting Needs

and Objectives

Economic Efficiency

Social Concerns

(public preference)

Environmental Impacts

Biophysical

Cultural

Socioeconomic

(includes health)


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Importance weighting for decision

factors

EXAMPLES OF IMPORTANCE WEIGHTING TECHNIQUES USED INENVIRONMENTAL STUDIES

Ranking

Nominal group process

Rating

Predefined importance scale

Multiattribute utility measurement

Unranked paired comparison

Ranked paired comparison

Delphi


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Ranking techniques for importance weighting

basically involve the rank ordering of decision

factors in order of importance. If n decision

factors exist, rank ordering involves assigning

1 to the most important factor, 2 to the

second-most important factor, and so forth,until n is assigned to the least important

factor. The rank order numbers can be

reversed.


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The Nominal Group Process (NGP) technique

(Voelker 1977) illustrates a ranking technique

The NGP technique is widely used in health,

social service, education, industry, and

government organizations.


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Rating techniques for importance weightingbasically involve assigning importancenumbers to decision factors and sometimes

their subsequent normalization via amathematical procedure.

Predefined importance scale(Linstone and

Turoff 1978) Multi-attribute utility measurement(MAUM)

technique (Edwards 1976)


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Predefined importance scales

Decision factors can be assigned numerical

values based on predefined importance scales

Use of the predefined scales can aid in

systematizing importance weight assignments


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Scale Reference Definitions

1. Very important A most relevant point

First order priority

Has direct bearing on major issues

Must be resolved, dealt with, or treated

2. Important Is relevant to the issue

Second order priority

Significant impact, but not until other

items are treated

Does not have to be fully resolved

3. Moderately important May be relevant to the issue

Third order priority

May have impact

May be a determining factor to major issue

4. Unimportant Insignificantly relevant

Low priority

Has little impact

Not a determining factor to major issue

5. Most unimportant No priority

No relevance

No measurable effectShould be dropped as an item to consider


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Multi-attribute utility measurement

(MAUM)

Can be used by an individual, a small group of

persons or multiple publics. Ten basic steps in

the MAUM technique are described follows:


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Step 1 Identify the person or organisation whose utilities are to be maximized

Step 2 Identify the issues to which the utilities needed are relevant

Step 3 Identify entities to be evaluated. They are outcomes of possible actions. But in a

sense, the distinction between an outcome and opportunity for further actions isusually fictitious.

Step 4 Identify the relevant dimensions of value for evaluation of the entities. It is

important not to be too expansive at this stage. The no:of relevant dimensions of

value should be modest, for reasons the will be apparent shortly.

Step 5 Rank the dimension in order of importance. The ranking can be done by

individual, by an interdisciplinary study team by representatives of parties having

conflicting interest acting separately or as a group.

Step 6 Rate the dimensions in terms of importance, preserving existing ratios. The

respondents will need to review previous judgments to make them consistent

with present ones.

Step 7 Sum the importance weights, divide each by the sum and multiply by 100.

Step 8 Measure the location for each entity being evaluated on dimensional yard stick

Step 9 Calculate utilities for entities .

Step 10 Decide if a single alternative is to be chosen.


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Paired comparison techniques (unranked andranked)for importance weighting involve

comparisons between decision factors and asystematic tabulation of the numerical results ofthe comparisons.

These techniques are used extensively in decision-

making efforts, including numerous examplesrelated to environmental impact studies.

Can be used by an individual or group, compareseach decision factor to each other decision factor in

a systematic manner.

If there are four basic decision factors F1 to F4, theuse of above technique is show below


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Factor Assignment of weight Sum FIC

F1 1 1 1 1 4 0.4

F2 0 1 0 1 2 0.2

F3 0 0 0 1 1 0.1

F4 0 1 1 1 3 0.3

F5 (Dummy) 0 0 0 0 0 0

10 1.0


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Scaling, Rating, or Ranking of

Alternatives

Scaling, rating, or ranking of each alternative foreach decision factor is the second major aspect inusing the multicriteria decision-making approach.

Examples of techniques include the use of thealternative profile concept, a referencealternative, linear scaling based on the maximumchange, letter or number assignments

designating impact categories, evaluationguidelines, unranked paired comparisontechniques, and functional curves.


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Alternative profile concept

for impact scaling

This concept is represented by a graphic presentationof the effects of each alternative relative to eachdecision factor.

Each profile scale is expressed on a percentage basis,ranging from a negative to a positive 100%, with 100%being the maximum absolute value of the impactmeasure adopted for each decision factor

If the decision factors are displayed along with the

impact scale from -100% to +100%, a dotted line canbe used to connect the plotted points for eachalternative and thus describe its profile.


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Scaling technique in which the actual measures ofthe decision factor for each alternative plan arenormalized and expressed as a decimal of thelargest measure for that factor. This techniquerepresents linear scaling based on the maximumchange

Letter scaling system incorporates eightyenvironmental factors oriented to the types ofprojects conducted by the U.S. Department ofHousing and Urban Development. The scaling

system assigns a letter grade from A1 to C2 for theimpacts, with A1 representing a major beneficialimpact and C2 an undesirable detrimental change


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Scalingfollows establishing an evaluation

guideline for each environmental factor. An

evaluation guideline is defined as the smallestchange in the highest existing quality in the

region that is considered significant

Functional curves, also called value functionsand parameter function graphs or curves, can

also be used in environmental impact studies for

scaling, rating, or ranking the impacts of

alternatives relative to decision factors.


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Decision-Focused Checklists

The Battelle Environmental Evaluation System

(EES) is a weighting-scaling checklist

developed for the U.S. Bureau of Reclamation.

It contains seventy-eight environmental

factors organized into seventeen components

and four categories as shown


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Another example of a weighting-scaling checklist for water resources projects is the Water

Resources Assessment Methodology (WRAM) developed by the U.S. Army Corps of Engineers


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Current Trends in Decision-Making

Tools

A recent trend in decision making in environmental

studies is the use of computer software. For example,

Torno et al. (1988) developed a training manual to

evaluate the environmental impacts of large-scalewater resources development projects.

A decision-support system computer model, called d-

SSYS, can help determine the relative weights ofevaluation parameters used to evaluate projects and

the utility function for each of the attributes

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Decision Methods

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