Both the cost and accuracy of parametric models vary widely. They are most likely to be reliable when the historical information used to develop the model was accurate, the parameters used in the model are readily quantifiable, and the model is scalable (i.e., it works as well for a very large project as for a very small one).
An analogous estimate is one that is arrived at by taking a project or part of a project that is already completed and adjusting the cost on the basis of size.
A bottom up estimate is a detailed estimate taking into consideration a number of small estimates and summarizing them to a total for the project or subproject being estimated. A top down estimate is usually ...