Yup. If you look at the factor your estimates are off, they&#x27;ll follow a lognormal distribution.<p><pre><code>   *
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And it&#x27;s natural, if you think about it, that any schedule which doesn&#x27;t include slack between tasks will almost certainly run long. (Even assuming you&#x27;ve got a mean of 0 -- as many tasks go short as go long --  you&#x27;re not going to get lucky enough that the tasks that go short do it &#x27;just right&#x27; to make up for the tasks that go long.)<p>So maybe include some slack.<p>Still, maybe you want to know how often will your schedule run long. So do some measurements of historical data to find out how your task estimates work out in practice.<p>Plug those in and do a few simulations, and viola, you can get a precise number of how you&#x27;re likely to do. Plus handy tool to evaluate schedule quality.