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Schedule Risk Analysis (SRA). Tariq Ashraf Systems Engineering Feb 24, 2005. Why SRA?. Prior to program execution, management needs to know what are the potential schedule road blocks ahead of him/her Establish warning indicators up front Build mitigation into the IMS during planning

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Schedule risk analysis sra

Schedule Risk Analysis (SRA)

Tariq Ashraf

Systems Engineering

Feb 24, 2005


Why sra
Why SRA?

  • Prior to program execution, management needs to know what are the potential schedule road blocks ahead of him/her

    • Establish warning indicators up front

    • Build mitigation into the IMS during planning

  • Deterministic model fallacy

    • Critical path based upon linked activities with the least amount of float

    • Assumes all linked activities are low risk – not true in real life


Risk impact on critical path

Deterministic Model

10 15 20 45

Program

Attention

Activity 1

Activity 2

Activity 3

15 10 15 40

Activity 4

Activity 5

Activity 6

10 10 20 40

Activity 7

Activity 8

Activity 9

Probabilistic Model

9-10-12 14-15-17 19-20-2251

Activity 1

Activity 2

Activity 3

14-15-17 9-10-12 14-15-1751

Activity 4

Activity 5

Activity 6

9-10-12 9-10-12 19-20-3458

Program

Attention

Program

Attention

Activity 7

Activity 8

Activity 9

High Risk

Activity

Activity X

Activity X

Potential Critical Path

Critical Path

Risk Impact on Critical Path


Brief objective
Brief Objective

Describe a structured methodology for conducting Schedule Risk Analysis (SRA)


Schedule risk assessment methodology
Schedule Risk Assessment Methodology

  • Two step process:

    • Step 1 : Assess and determine the risk level of each IMS activity to identify activities that are high or moderate/medium risk – the most important element of SRA

    • Step 2 : Determine potential impact of the High/Moderate risk activities on program events using a simulation tool


Step 1 how to determine the risk level of an activity
Step 1. How to Determine the Risk Level of an Activity?

  • Assess each activity against the elements that impact the activity

    • The activity model provides the answer


Activity model

Input

Activity Model

Dependency

Activity


Input dependency one predecessor

Ps = Probability of Success

Activity 1

(Ps = 80%)

Activity 2

Input Dependency – One Predecessor

Ps = 80%


Input dependency multiple concurrent predecessor

Cumulative Ps

80% x 80% x 80% x 80% = 41%

Activity 1

(Ps = 80%)

Activity 2

(Ps = 80%)

Ps = 41%

Activity 5

Activity 3

(Ps = 80%)

Ps = Probability of Success

Activity 4

(Ps = 80%)

Input Dependency – Multiple Concurrent Predecessor

The greater the number of concurrent predecessor activities,

the lower the Cumulative Probability of Success


Activity model continued

Input

Activity Model (continued)

Dependency

Activity

Source

Timeliness of input is dependent upon

control exercised over the input source


Activity model continued1

Input

Resource

Activity Model (continued)

Dependency

Activity

Source

Constraint


Resource constraint

Theory of Constraint

Elapsed Time

Activity 1

Productive Work

Resource A

Activity 2

Non Productive Work

Setup

Work on Task

Suspend

Resource Constraint

There is a loss in resource efficiency when a resource

is applied to multiple concurrent activities


Activity model continued2

Process

Input

Output

Resource

Activity Model (continued)

Maturity

Complexity

Dependency

Activity

Source

Expectancy

Environment

Source

Constraint

State


So now what
So Now What?

  • Develop a likelihood rating matrix for each activity element

    • Example:

      • Input Dependency

        • 1 – No Predecessor

        • 5 – N Concurrent Predecessors

      • Resource State

        • 1 – Existing

        • 5 – New development using state-of-the art



So now what1
So Now What?

  • Now that the activity elements have been identified develop a likelihood rating matrix for each activity element

    • Example:

      • Input Dependency

        • 1 – No Predecessor

        • 5 – N Concurrent Predecessors

      • Resource State

        • 1 – Existing

        • 5 – New development using state-of-the art

  • For each activity

    • Using the likelihood rating matrix, determine the level for each activity element

    • Determine the schedule consequence using the criteria provided in the risk plan

    • Determine the activity risk level by mapping highest likelihood level to schedule consequence

  • Establish Max-Min durations criteria for high, moderate, low risk activity

    • Durations

    • + of % of ML


The risk level determines the estimate confidence and duration spread min ml max of an activity

The risk level determines the estimate confidence and duration spread (Min-ML-Max) of an activity


High risk activity

Most Likely duration spread (Min-ML-Max) of an activity

Max

Min

Duration Spread

Low

Confidence Level

High

High Risk Activity


Moderate medium risk activity

Most Likely duration spread (Min-ML-Max) of an activity

Min

Max

Duration Spread

Low

Confidence Level

High

Moderate/Medium Risk Activity


Low risk activity
Low Risk Activity duration spread (Min-ML-Max) of an activity

Most Likely

Min

Max

Duration Spread

Low

Confidence Level

High


Step 2 determining the impact of high moderate risk activities on program event s
Step 2. Determining the Impact of High/Moderate Risk Activities on Program Event(s)

  • Review the IMS logic for the following:

    • All activities are linked

    • The logic makes sense

  • Maximize FS relationships. Simulation models do not like other relationships (SS, SF, FF). Also minimize lags in the activity logic i.e. FS+20, FS-20, etc.

  • For each activity, input estimates (Minimum , Most Likely, Maximum ) based upon the risk level of the activity and run simulations

  • Out put generated by simulation tool

    • Probability vs. Time curve for each event selected for analysis

    • Criticality Index for each task (during the simulation, the number of times an activity fell on the critical path)

  • Results from the first simulation may not meet expectation

  • Adjust IMS and reiterate


Conclusion
Conclusion Activities on Program Event(s)

  • Risk is inherent in a complex system with multiple stakeholders

  • Prior to execution, management must know what risks are embedded in the IMS

  • Applying a structured methodology ensures schedule risk is identified consistently by all stakeholders

  • Analysis is time consuming and requires input from all stakeholders but the value cannot be underestimated


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