Effort Estimation

What are we trying to answer?

How many hours of effort will this project take?

How much will it cost to deliver this project?

Approximately how long will it take?

Estimate

To form an approximate judgment or opinion regarding the worth, amount, size, weight, etc., of;

calculate approximately:

Cone of Uncertainty

Estimation Techniques

Counting

expert judgment (individual and group)

Decomposition

Analogy

proxy estimation

planning poker

and wall estimation.

Wall estimation

Decomposition

Task decomposition refers to the whole-part composition structure of a task model.

NGSOFT

• measure it in days• Nothing gets done in less than half-a-day

Unit of Measure

Seconds, Days, Months, Years

Story points

What does AGILE/SCRUM say?• Product backlog estimates are in points (fibonnachi)• Sprint backlog estimates are in hours.

NGSOFT:• We have not yet found customers commited enough to use

story points (except Telmap and MOD).

Risk and buffer

And

AND

AND?!?!?!?!?!

Risk

Risk is the probability of a significant negative impact on the project.

Special causes contribute the risk to the project.

You manage special causes by

• Avoiding them• Mitigating their effects

You should identify risk long before the task is ready to go

Buffer

Project Buffer: Create a buffer for the project.

Feeding Buffers: Create a buffer for each task that feeds into the critical chain.

Re-level the resources to account for buffering changes to the plan

Calculating buffer

Rule-of-thumb method: one-half the length of the chain the buffer terminates

Sum of Squares method: sum the squares of the task lengths, then take the square root

NGSOFT

• Systems – 25% of total project cost (without management, which is another 10%)

My XP

The more people estimate the task, the closer it is to real workdays (estimation is better)

The more people estimate the task, the more consensus we have over the estimation (team commitment is better).

The more people meet to plan the task – the more we learn about what needs to be done (works BEST IF you have a QA member).

Don’t be afraid to requestion your reasoning (Sometimes we don’t know/grasp what we are trying to estimate).

Now let’s go through the template and make some changes to it