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Chapter 6: Resource and schedule estimating. - Coggle Diagram
Chapter 6: Resource and schedule estimating.
Resource Planning
Starting with a program size estimate, you use the methods described in this chapter to estimate the time the work will take. Judge the accuracy of this estimate, and generate a schedule.
PRODUCTIVITY
Productivity is generally measured as the labor hours required to do a unit of work. When calculating productivity, you must consider, for example, the unique conditions of each job and the quality of the resulting product.
Each project is different. If you lump all project activities into some global productivity number, you will eliminate much of the thought required to produce a good plan.
Estimating Development Time
PLANNING DEVELOPMENT TIME
One of your first planning concerns is selecting the historical data to use. Basical- ly, your choices are as follows:
A: Use data on estimated object LOC and total actual development hours. This is your best choice because it represents the way the PROBE method produces the estimates.
B: Use estimated new and changed LOC and actual development hours. This is your choice if you do not have enough data for choice
C: Use data on estimated or actual new and changed LOC and actual hours. If you do not have the data for either choice A or B. you must use choice C
To select among the choices follows:
Do you have historical data?
Determine whether there are sufficient estimated object LOC data for a re gression calculation
Determine if there are sufficient estimate data available for a regression calculation
Calculate your historical productivity in LOC per hour.
Calculate the time required for the new program.
Calculate the shortest and longest likely times.
Determine the time estimate and range.
Do the regression calculation for estimated new and changed LOC and actul hours
Calculate the time required to develop the new program.
Calculate the prediction interval for this estimate.
Determine the time estimate and range.
Do the regression calculation on estimated object LOC to development hours
Calculate the time required for the new program
Calculate the prediction interval for this estimate.
Determine the time estimate and range.
LOC Size
Estimating Task Time
The following steps are numbered
Ensure you have a clear statement of the requirements for the task to be done.
Do you have a defined process for the task?
If your answer to step 2 is no,it must include planning and postmortem steps. It should also divide the work into elements that are between about 10 percent and 25 percent of the total job
Do you have defined process measures?
If your answer to step 4 is no, you need to define at least size and resource measures.
Do you have historical data?
Even if your answer to step 6 is no, you can usually identify some similar jobs and judge how long they took.
Are sized-based resource estimates appropriate?
If the answer to step 8 is no. you must make an intuitive estimate based on comparison with other work.
Estimate the maximum and minimum times the job will likely require.
Determine the likely estimate range.
12., 13., 14. Follow the PROBE method to produce the estimate and the prediction interval.
Combining Multiple Estimates
You don't just add the standard devia tions: you add the variances
THE PREDICTION INTERVAL FOR COMBINED RESOURCE ESTIMATES
If you have calculated a prediction interval for each case and if all these intervals were gener ated in the same way, you can treat them as standard deviations and combine them.
COMBINING PROBE-GENERATED PREDICTION INTERVALS
Here, you would get the same B, and B, regression parameters for each of the separate component estimates. You would still get the total estimate by adding the individual estimates, and you would use the same prediction interval calculation.
Using Multiple Regression
You can overcome the lack of data in one way by using the statistical tech- nique called multiple regression, which enables you to estimate the relative con- tributions of the work on the new, reused, and modified code in the total development hours.
Schedule Estimating
THE SCHEDULE ESTIMATING PROCESS
The schedule estimating process requires a detailed estimate of the hours needed to do the total job. You then allocate these hours to the various project phases.
DIRECT PROJECT TIME
Divide your week into what you consider to be your key activities. For the PSP work, use the project plans. For other activities
THE UNPLANNED TIME CUSHION
When you work in a software organization, you will find that the amount of time you can devote to direct work will fluctuate considerably.
MAKING THE SCHEDULE
Resource Estimate
Estimate the task hours.
Historical utilization data Based on your historical records
Set utilization factor.
Calculate the available hours.
Determine your other commitments.
Plan your available project time per week.
Plan the task sequence.
Set the task schedule
Earned Value Tracking
Earned value tracking is a way to evaluate project progress. It establishes a relative value for every task and credits that value when you complete the task