Analogous Estimation (Top-down)
Can ensure no work is inadvertently omitted from work estimate
Can sometimes be difficult for lower-level managers to apportion cost estimates.
Is very accurate and gives lower-level managers more responsibility.
May be very time consuming and can only be used after the work breakdown structure (WBS) has been well defined.
Using parametric model is not time consuming.
May be inaccurate depending on the integrity of the historical information used.