Coin Toss 101

As an experiment, toss a coin 100 times. Let heads represent one estimate of the duration of a project task, say writing a specification, of 10 days, and let tails represent an estimate of duration of 15 days for the same task. Both estimates seem reasonable. Let us flip a coin to choose. If the coin were "fair" (that is, not biased in favor of landing on one side or the other), we could reasonably "expect" that there would be 50 heads and 50 tails.

But what of the 101 ^st toss? What will it be? Can we predict the outcome of toss 101 or know with any certainty whether the outcome of toss 101 will be heads or tails, 10 days duration or 15? No, actually, the accumulation of a history of 50 heads and 50 tails provides no information specifically about outcome of the 101 ^st toss except that the range of possible performance is now predictable: toss 101 will be either discretely heads or tails, and the outcome of toss 101 is no more likely to come...