EdTrice: ah! thanks!

that explains something i have been wondering about for some time already :)
i have played more games of hyper gammon than backgammon (323 vs 255) but still my hyper gammon bkr changes a lot while my backgammon bkr behaves exactly like described below (8-13 points difference depending a bit on how many i won/lost in succession lately)

of course my hyper gammon has a much higher deviation :)

taking the deviaton into account can explain both the effect of hyper gammon vs backgammon as well as the effect of a lot of wins in succession


i asked for the formula as well and thought i found it via google .. but then someone else (i forgot who and on which board :)) posted the correct link with the correct formula (fencer responded with 'yes' i think ;)) .. it might be the one pedro posted as well :)