In my previous TechRepublic article, I described how to estimate costs across a project using a top-down approach with an apportion method. Top-down estimating and allocation is useful when you're estimating similar projects; however, a bottom-up estimate will yield a more accurate estimate. The trade-off with a bottom-up estimate is the amount of time required to deep dive the requirements and estimate the lower levels of the work breakdown structure (WBS).
In this tutorial, I'll show you how to develop a bottom-up estimate using Matchware MindView Business edition's roll-up feature.
Open your WBSI'll use the same WBS (see Figure A) as I did in the last tutorial, except I'll estimate costs at the lowest level. (You'll need MindView to open the sample WBS file, so download the mind-mapping software's evaluation copy and follow along.) Figure A
Use this sample WBS. (Click the image to enlarge.)
Step 1: Expand the entire WBS
In order to conduct a bottom-up estimate, we need to evaluate costs at the lowest level of the WBS.
- Open MindView and the attached sample WBS.mvdx file.
- To expand the WBS, go to View | Detail Level | Show All Levels (Figure B).
Expand WBS. (Click the image to enlarge.)
Step 2: Assign project costs at the lowest level of the WBS
The next step is to assign project costs, starting at the lowest level of the WBS.
- In the Implementation branch, navigate to the Portal Configuration node and click it.
- Click the Calculation tab.
- Enter Budget for the branch value.
- Assign a value of $30,000.
- Repeat this process for each node in the Implementation branch (Figure C).
Once the branch values are assigned at the lowest level, we will use a unique roll-up feature in MindView to calculate the total at the node level.Figure C
Assign project costs. (Click the image to enlarge.)
Step 3: Assign a SUM formula to the summary node
- Click the HR Operations node in the Implementation branch.
- Instead of assigning a numeric value, enter the word SUM (Figure D). This will sum all the Budget branch values in all the sub-branches under HR Operations.
- Repeat this procedure for all the nodes in the Implementation branch.
Assign SUM to the Budget field. (Click the image to enlarge.)
Step 4: Assign the SUM formula to the Implementation node and Top Level node
The next step is to assign the same formula to the Implementation and root ERP Implementation node.By assigning the SUM formula to every node, you'll quickly build an automatic roll-up based on the lowest level data (Figure E). If you want to select specific nodes, you can click a node, press [Ctrl], and then click other nodes. The Quick Data panel will show the Sum, Avg, Min, Max, and Count values based on the number of nodes selected. Figure E
View rollup project costs. (Click the image to enlarge.)MindView's branch value is a unique feature that incorporates fully functional formulas that help project managers forecast budgets, track costs, and estimate work. By allocating budget values across the WBS and rolling up the values, you can quickly calculate a bottom-up estimate. Once the Implementation node is completed, apply the same formulas and assign values to all the other nodes in the WBS. Once completed, you should have an estimate that looks similar to Figure F. For viewing purposes, the WBS is rolled up to the second level of detail. Figure F
You now have a completed WBS with total cost estimate. (Click the image to enlarge.)
I often use the bottom-up approach with MindView to develop detailed estimates. Even in this example, the WBS is defined only to three levels, although I recommend doing further definition to improve estimation accuracy. The major trade-off is the amount of time a team spends planning and estimating costs versus funding a high-level estimate and starting the project. Using a WBS for either a top-down or a bottom-up estimate is a helpful tool in any project manager's toolkit.