Confused in "analogous estimating" method

I'm confused in the "Analogous estimating" method

in PMBOK 4th version, page 171 states that "analogous estimating uses the value of parameters, such as scope, cost, budget, and duration or measures of scale such as size, weight, and complexity, from a previous, similar project as the basis for estimating the same parameter or measure for a current project."

1. From the definition, it's very much we need to use the actual historical data for it. However, in Rita's book 6th edition, question 5, page 250, the choice "Analogous estimating use historical data" is not a correct choice.

2. in my experience, I usually use Analogous estimating as bottom-up approach, but not sure why it seems PMBOK promote this method as "top-down", which I feel quite unconfortable and don't know how what to call the estimating way that I'm doing so far (as I also try to use the same term that PMI promote)

 

Any advise on this?

Thanks

Binh

 

1- Parametric estimation is the one that uses Historical data, not Analogous estimation.


 


2- Analogous estimating is always a High level estimation (Top-Down) & not a detailed bottom-up.

Hi Binh,


Analogus is for sure uses historical data. However, rita's question was little twisted and she used the word


"Detailed Actual Historical Data" . We never use the detailed actual data as it is. It always gives you a rough estimation.


 We use that as a reference and  new


estimation is based on it. It always uses TOP-DOWN approach. Get the big whole data and then


break it down and go step by step down, till you get it detailed enough.


-Bish


 


 

Thanks Bish and all, I'm clear now!

Hi,

You can read this article http://www.pmbypm.com/analogous-parametric-estimation/ to understand the difference with examples.

BR.