Project Management Knowledge (2010) has it that bottom -- up estimating each task is broken down into smaller components and then individual estimates are developed in order to determine what is actually needed to meet the requirements of each of these small components and finally a sum of the total estimates is done. Liming Wu (1997) indicates that bottom-up is time consuming which shows that in instances where time factor is limited top-down estimation method is preferred because it is not time consuming. Depending on the circumstances surrounding a project is what determines which method is much preferred. However because bottom-up estimation method tends to involve all the components costs of a project usually it is preferred to top-bottom method. More so this is so because it allows careful consideration of each of the smaller parts which makes it typically far more accurate than the top-down estimation method.

In cases where detailed information for justifying estimates is required bottom-top method is preferred because it gives the detailed information required which top-bottom estimate method does not offer. In cases of limited personnel Liming Wu (2007) top-bottom estimation method is better than bottom-top estimation method since it requires fewer personnel to do the calculations and make the estimates. All in all depending on the circumstances surrounding the project it is what determines which method is appropriate.

Student 2

Top-bottom estimation method involves overall cost analysis of a project and then breaking down the project cost according to work packages. Bottom-top estimation method involves calculating the costs of each work package in a project and then making an overall cost summation to know how much the project is going to cost. Bottom top estimation method is much preferred because it gives a more accurate estimate...

Where all the relevant information required to rate each work component is not available, indeed a top-bottom estimation method is much more appropriate to use than bottom-top method.
Student 3

Estimation methods are various but for this case top-bottom and bottom-top estimation methods are the ones of essence. Top-bottom estimation entails global outlook of a project and wholesome estimation and then subdividing the cost according to the different project components. On the other hand bottom-top estimation entails calculation of the worth of the various work components and then aggregating them to get the total cost of the project. Where justification of the estimated cost of the project is of essence, the bottom-top estimation method is preferred to the top-bottom estimation method which avails no details of how the estimate has been reached to. Top-bottom estimation method is so good where there is need to redeem time as compared to the bottom-top method.