Discrete v Continuous VP Scales

JeremyChild

We are considering moving to using the WBF continuous IMPS to VP scale for congresses, as it eliminates most draws, and (we think) is a little more exciting.

What factors should be considered when deciding which to use?
What do other congresses do?
If using the continuous scale, what do you put in your scoring booklet (if anything)?

Thanks

JamesC

I think I prefer watching to see if the discrete scores tip over one, but it's also good to experiment.

For the scoring booklet I think you'd probably put the information on what's a 20-0, 19-1, 18-2 etc, and a note that it's a continous scale. Maybe just 15-5 and 20-0. How do the WBF describe their scales?

JeffreyS

In my opinion, bad Idea! The discrete scale offers a simplified approach and is more user-friendly, particularly for local tournaments and manual scoring. Its simplicity of whole numbers means the players can check more easily, is more precise for small Imp margins, and fits with concavity rules.

You may also find with Continuous people more likely to appeal against results since every Imp makes a difference!
While the continuous scale may be preferred for WBF championships for its precise calculation (every IMP counts equally), the discrete scale is designed for situations where ease of use is paramount while maintaining the mathematical soundness.

gordonrainsford

@JeffreyS said:
is more precise for small Imp margins,

I don't understand how

You may also find with Continuous people more likely to appeal against results since every Imp makes a difference!

The point is that every IMP should make a difference.

While the continuous scale may be preferred for WBF championships for its precise calculation (every IMP counts equally),

Not equally

the discrete scale is designed for situations where ease of use is paramount while maintaining the mathematical soundness.

What do you mean by mathematical soundness, in this context?

JeremyChild

Is there a continuous MatchPoint percentage to VPs scale (for swiss pairs)?

If there is, I can't find one - but I see no reason why one couldn't exist.

Robin_BarkerTD

@JeremyChild said:
Is there a continuous MatchPoint percentage to VPs scale (for swiss pairs)?

My responsibility for the White Book and the EBU VP scales started in 2013, when the WBF VP scales were adopted. Neither at that time nor subsequently was there any development of a decimal VP scale for match points.

The old EBU VP scales for IMPs were built on the principle of all 21 match outcomes were equally likely - the new WBF VP scales are built on different principles. The old (current) VP scales for match points were built on the same principles of all outcomes being equally likely.

I think the simplest way to create decimal VP scales is to pick a cap for the master points for a match (50% + X%) and then scale the capped result and round to 2dp. round(20(M - X))/(2X),0.01)

I guess that cap should depend on number of boards in a match but capped at 70% (X=20) gives very simple formula.