Tips to validate a development estimate

If you have historical data, you may as you stated use it as a basis of comparison. In that case, I tend to find a typical range (mean value and standard deviation). If an estimate is within that range, about all the comparison can tell you is it is consistent with previous performance.

The other thing you might consider is a non-advocate review. This is where you bring in some independent reviewers with more technical knowledge to ask the more difficult questions. If they don't have an existing bias such as "I made this estimate myself so I'm pretty sure it's accurate." then they are more likely to evaluate the inputs objectively.

I usually ask the estimator to provide assumptions, risks, contingencies that are built in or associated with the estimate.Then I ask questions until I am satisfied that the estimate is reasonable. You do ask for an estimate range, right?

Jose -

in the absence of expert judgment (related to the specific context of the project in question) or sufficiently similar historical data, you won't be able to improve estimation accuracy so a better approach might be to make small bets by using an adaptive approach where you try to surface and tackle the areas of greatest uncertainty early on to increase confidence in the team's approach.

Kiron