Why are construction delays described as fat-tailed?
Because most jobs overrun by a little, but a small number overrun by a lot, far more often than a bell curve would predict. Studies of construction schedule overruns found the data are skewed and non-Gaussian, and research on IT projects and the Olympics found power-law tails. In practice this means the average delay understates the risk: a few bad outcomes dominate the expected cost.
From the RRD Field Guide, checked against the sources cited in Cheapest Quote vs Delay Risk: The Economics of Choosing a Contractor in Singapore. General information, not advice for your project.
The fuller picture
The cheapest quote is only cheaper if the job finishes on time and on scope. Overrun research shows delays are common and fat-tailed, so a small price saving can be wiped out by a few weeks of rent, lost revenue or holding-over. Compare quotes on expected total cost, including probability-weighted delay cost and the worst plausible outcome, not the tender price alone.