Estimating involves forecasting the time and cost to complete project deliverables. There are two main types of estimates: bottom-up estimates require more effort but rely on those familiar with the work, while top-down estimates can be made by managers without direct experience. Software cost and effort estimation is not an exact science due to many variable factors. Key parameters that affect estimates include resources, time, human skills, and cost. Common software estimation techniques include top-down and bottom-up methods such as the three-point estimation technique.

3.  Estimating
◦ The process of forecasting or approximating the time and cost of
completing project deliverables.
◦ A rough calculation of the value, number, quantity, or extent of
something.
 Types of Estimates
 Bottom-up (micro) :require more effort to develop & rely upon those who
understand the work to estimate specific work activities
 Top-down (macro) :derived from experience to estimate project duration and
total cost. Could be made by a manager with no direct experience of the
processes to complete the project.

5.  Software cost and effort estimation will
never be an exact science.
 There are too many parameters, e.g.,
human, technical, environmental, and
political parameters, that affect the actual
estimation making it almost impossible to
have considered all cases.

9.  Resources: Resources are required to carry out any project
tasks. They can be people, equipment, facilities, funding,
or anything else capable of definition required for the
completion of a project activity.
 Times : Time is the most valuable resource in a project.
Every project has a deadline to delivery.
 Human Skills : Human skills mean the knowledge and
the experience of the Team members. They affect to your
estimation. For example, a team, whose members have
low testing skills, will take more time to finish the project
than the one which has high testing skills.
 Cost: Cost is the project budget. Generally speaking, it
means how much money it takes to finish the project.

10. List of Software Estimation Techniques
 Top-down Methods
 Bottom-up Methods
 Work Breakdown Structure
 3-Point Software Estimation Technique
 Function Point Analysis
 Multiplication Method
 Analogy Method

12. Scoping:
”Project scope is the part of project planning that involves
determining and documenting a list of specific project goals,
deliverables, features, functions, tasks, deadlines”
 You need first to scope the project even if you do
not have the full detailed requirements but you can
assume some of them.

13.  Decomposition:
 Break your software into smaller components and functions,
 This is similar to work breakdown structure but only for the software
components not all the working activities for the software.
 You may also collect different data from the project team or the
customer to ensure that you have listed all functionalities.

14. Sizing:
 In this step the actual estimation will be done for each component
alone
There are different techniques which you can apply
to estimate the effort for tasks but we use 3-Point
Software Estimation Technique to calculate total effort.

15.  Three-Point estimation is one of the techniques that could be used to
estimate a task
 The simplicity of the Three-point estimation makes it a very useful
tool for a Project Manager that who wants to estimate.
 In three-point estimation, three values are produced initially for every
task

17. Let’s see how to use the above three values in the following example.
 The best case: To complete this task is 120 man-hours (around
15 days). In this case, you have a talented team, they can finish the
task in smallest time.
 The most likely case: To complete this task is 170 man-hours
(around 21 days). This is a normal case, you have enough resource
and ability to complete the task.
 The worst case: To complete this task is 200 man-hours (around
25 days). You need to perform much more work because your team
members are not experienced.

19.  In the above estimation, you just determine a possible and not
a certain value, we must know about the probability that the
estimation is correct. You can use the other formula.

20.  In above formula, the SD mean Standard Deviation, this value could
give you the information about the probability that the estimation is
correct.
 To complete the task , you need 166.6 ± 13.33 Man-hour (153.33 to
179.99 man-hour)

21.  After initial estimate, you will need at some point to ask for
expert opinion for some new functionalities you may not
aware off, or for considering a review from your peers that
you have done the correct estimation.
 Just to ensure that you are on the correct path.

22.  This can be considered the final step as you
aggregate all the estimations from all
components and function.
 You can go another round across the process
until reaching the correct estimate which will
be approved by the Project team and the
Management as well.

23.  Performance Models
 Optimal Performance