What’s the difference between Analogous and parametric Estimating?

Thanks all.

What I notice about the clarifications is the word “parameter” is not a part of analogous explanation. Although PMBOK includes it and causes confusion.

So say you want to use the labor hours from a past similar project. That will be analogous right?

Thanks all.

What I notice about the clarifications is the word “parameter” is not a part of analogous explanation. Although PMBOK includes it and causes confusion.

So say you want to use the labor hours from a past similar project. That will be analogous right?

Thanks Rami.

Refering to hours of the project in total although analogous can be used for components too. And not necessarily top-down.


Let’s say the project is painting a house.

Now let’s say you have three of such similar houses you have painted in the past and each took slightly different times.

So in estimating for the current project you rather use the average hours of the three past project.

Average is a statistical measure. Parametric definition, other than the key words historic and parameter, also includes statistical and algorithm.

So in this average of three past durations case is it now parametric or even three point.

This is the finally of my question. I wanted to build it up a bit more gradually.

The nuances in the definitions and how to really dichotomize. Great contribution from all.

Richard

This is a grey area really here. Three point estimate is usually taking the average for three results of the same activity. You are more or less doing the same for for different projects, it can still be three point estimate and at the same time analogous as you are comparing the big picture here high level. I wouldn't consider it parametric.

In reality, there is no black and white in estimates, it can be a mix of many methods all together.

However, for the PMP, exam, if that is your concern, you have to give it your best judgement based on your experience.

Hope this helps.

RK

Three point estimates do not use 3 random figures but specifically pessimistic, optimistic and most likely data points.

For analogous estimates you could use the average of previous similar projects.

I came up with a few bad examples before a good one. Between that and reading the comments of my colleagues, if teaching a class I would explain the difference as follows: An analogous estimate is based on an analogy, while a parametric is based on a correlation between 2 or more variables (parameters).

An analogy compares 2 different things that are similar in some way. We can approximate what we need to know about one thing, from what information we have about the other thing. It can be a rough parametric such as, “This job is about equivalent to doing that job twice.”, but not as precise as, “This job is equivalent to 2.14 X that job.”

A parametric uses one or more parameters (variables) to calculate different ones. It could be based on a logical relationship such as Mass = Volume * Density. Those variables are related, but entirely different properties. Knowing 2, we can calculate the 3rd. They can also be a heuristic (something we use because we know it works), based on experience such as many data points.

My favorite example of a heuristic: The cost of some products is primarily driven by the engineering design effort. It turns out the cost correlates very closely to the product weigh however, so if I know the weight, I can calculate both the cost and the engineering effort to design it. There is no logical reason why it works, but it does so we can create a precise estimate, based on a completely unrelated variable.