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Nigel Merrigan's new formula explained

Posted By: Timothy Chow
Date: Monday, 25 July 2011, at 1:31 a.m.

I recently announced that Nigel Merrigan had recently updated his article on the Metric Formula. Some people may have found Merrigan's article difficult to understand, so I am giving a brief summary here.

Merrigan gives a new formula for estimating the DMP winning chances for the leader in a long non-contact race. I will explain his formula in the special case where wastage can be ignored. (Merrigan explained to me in a private email that he does have systematic methods for handling wastage, but they are not explained in the current version of his article; perhaps the next version will contain those details.)

The first step is to look at the leader's pip count and determine how many pips behind the trailer can be, and still have a valid money take. This number Merrigan calls "PLT" (for "point of last take"). The value of PLT can be computed using Trice's "Rule of 62" or something like it, e.g., the Nack58 rule. For example, if the leader's pip count is 83 and there is negligible wastage, then PLT = 10.

Next, we plug the value of PLT, as well as the value of L (defined to be the difference in pip counts between the leader and the trailer), into the Metric Formula:

50 + L*(62 – PLT)/(PLT + L)

Continuing our example, suppose the leader's pip count is 83 and the trailer's pip count is 99. Then L = 16 and the Metric Formula yields a value of 82.

The final step of Merrigan's recipe is to add E-Pips. To compute E-Pips, first count (for each player) how many pips it would take to bear in all the outfield checkers to the 6pt; take the trailer's "pips to the 6pt," subtract the leader's "pips to the 6pt", and multiply by 0.21. Then count how many extra crossovers the trailer has, and add 0.5 for each extra crossover. For example, suppose the trailer needs 9 pips to bear everything to the 6pt and needs 4 crossovers, while the leader needs 4 pips to bear everything to the 6pt and needs just 1 crossover. Then the E-Pip total is 5*0.21 + 3*0.5 = 2.55. Adding this to the previously calculated value of 82 from the Metric Formula yields 84.55. That is, in this situation, the leader has an estimated 84.55% chance of winning the race at DMP.

Messages In This Thread

• Nigel Merrigan's new formula explained
  Timothy Chow -- Monday, 25 July 2011, at 1:31 a.m.
  • Nigel Merrigan's new formula explained
    Tom Keith -- Monday, 25 July 2011, at 12:42 p.m.