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Flashcards in POM L9 Deck (20):

What are the components of estimation?

- Cost: Personnel (in person day, person days x cost rate), Material, Extra costs
- Scope: Number and Complexity of requirements
- Time: Development time (duration = effort/people ), project duration, dependencies
- Infrastructure


Top-Down and Bottom-Up estimation

Top-Down Approach
• Estimate effort for the whole project
• Breakdown to different project phases and work
Bottom-Up Approach
• Start with effort estimates for tasks on the lowest possible level
• Aggregate the estimates until top activities are reached

top-down if you don't have WBS (Work Breakdown Structure), bottom up if you do


What are the problems with Traditional Estimation Techniques

- focus on the completion and not on delivery of features
- wrong focus in schedules review (reviewers look for overlooked activities not features)
- saving time through reducing quality


Dependency Diagrams

formal notation that helps in analysis of complex schedule
Consist of
- Event
- Activity (amount of work)
- Span time (amount of time, parameters: availability of resources, parallelizability of the activity)


Critical Path (forward path analysis) and Slack time (back path analysis) in dependency diagrams

- critical path: sequence of activities that take the longest time to complete

- Noncritical path: a sequence of activities that can be delayed and the project can still finish in the shortest time possible

- Slack time: the maximum delay time


Path Types in Dependency Graphs

Critical path: path in which all slack times are zero
Noncritical path: Any path with at least one nonzero slack time activity
Overcritical path: at least one activity has a negative slack time


Types of Dependencies

FS (Finish-to-start): B cannot start till A finishes
SS: B cannot start until A starts
FF: B cannot finish until A finishes
SF: B cannot finish until A starts


Start and Finish Dates

- Earliest start date (ES)
- Earliest finish date (EF)
- Latest start date (LS)
- Latest finish date (LS)


Dependency constraints

- As Soon As Possible (ASAP)
- Start No Earlier Than
- Start No Later Than (SNLT)
- Must Start On (MSO)
- As Late As Possible (ALAP)
- Finish No Earlier Than (FNET)
- Finish No Later Than (FNLT)
- Must Finish On (MFO)


What's milestone view specially good for

Good for introduction of project and high executive briefings


Activities view

Good for documentation and during developer meetings


Two types of Gantt chart

- Person entered view (when managing experienced teams)
- Activity centred view (to identify teams working on same activity, when managing beginners)

Gantt chart is easy to read, and when combined with milestones is good for reviews


PERT (Program Evaluation and Report Technique)

• Assign optimistic, pessimistic and most likely estimates
for the span times of each activity
• Compute the probability that the project duration falls within specified limits
allows to use multiple estimates per project activity

Good for clear illustration of task dependencies


Fudge factor

A fudge factor is the extra amount of time you add to
your best estimate of span time “just to be safe”
Don’t use fudge factors!
Reason: Parkinson’s law


Backing In

You start at the last milestone of the project and work your way back toward the starting milestone, while estimating durations that will add up to the available time


What is COCOMOD and what are its problems ?

COnstructive COst MOdel
#Top Down Approach to estimate cost, efor n schedule based on size and complexity
#Comparing with finished project
#No Req. changes during development.
#• Calculate effort
• Effort = A * KDSIB
• Calculate development time
• Time = C * EffortD
-Judgment is required
-Estimation can differ by the factor of 4 (Cone of uncertainty)
-Some important factors are not considered (Skill, travel ...)


Explain the Playing Poker approach !

Estimation of the difficulty of a project, Each memer gets to choose a difficulty level of a task then the result of all is show it repeats itself till every one agree on a same result
+wisdom of crowd
-long discussion


Why is estimation a hard task?

#Discussions may take long time
#There is not enough knowledge about the developing environment


What does the Cone of Uncertainty show?

#There is not enough knowledge about the project at the beginning
#Many characteristics of a project become clear only after some time
#estimation results can deviate from actual effort by a factor of 4.


What should be considered when estimating?

#Project budget
#The locations where development takes place
#Project duration