Estimation Quiz

Given some instructions, provide an estimate for the process of assembling a shelf (see picture below).

Academic approach

After spending several minutes thinking, you estimate it to 30 minutes and  then start assembling the parts in order to build the shelf.

Pragmatic approach

Depending on the complexity of the assembling and the quality of the given instructions the whole process can fall out of any estimation.

..and from the initial estimate of 30 minutes you can end up in a 10 hours of actual work.