New Problem Selection Algorithm?

[tmr]

Any change to the problem selection algorithm? 

My rating is up about 100 points over the last week.  Maybe its just part of the random nature of the selection process but recently I've been given a long string of fairly easy problems or higher ranking problems that seemed pretty easy.  Then today I got several high ranking problems that I've had before (I missed them the last time I got them but not this time; I study almost every problem I miss and while my memory isn't great I usually remember the theme for these and can avoid mistakes).  In all for the last 35 problems I've only missed 4 whereas since the late May update my percentage was pretty close to 50%.  Seems like something must have changed.

I suppose if it is all part of the random process I'll be due soon for a long string of misses.  I'm not looking forward to that.

[richard]

Hi tmr,

Not a change in the selection algorithm, but a very big change in the problem set (see news on front page and in "News" section of forum).

Lots of problems have completely new ratings (starting rating of these problems is determined by a regression equation estimating rating based on length of move sequences), another large bunch of problems are replacements for old problems but with alternative moves marked.  The later set will currently be "easier" than their rating as they allow alternatives and therefore will not be failed as often. The RD of these new replacement moves is high so they should adjust fairly quickly to their appropriate rating levels.  I would expect the overall set to be slightly easier due to the alternatives, but individual users may not notice this (after problem ratings resettle) if there is enough hard problems remaining to serve up.

Regards,
Richard.

[tmr]

Thanks.  I don't think this is the cause of what I've been seeing since it started on the 13th a few days before your recent update.

I have noticed the effect of the new problem set.  I looked through the problems I did between June 3 through 11 and noticed that almost all of the one I missed have either been disabled or have been replaced with an alternative line problem.  Don't know, but I suspect that this would result in an easier problems set.  Probably less frustrating though.

[richard]

If you noticed it on the 13th then I think it is more likely just a statistical blip as there were no changes impacting problem selection around that date. 

In theory the problem set will not necessarily get easier. The problems that were hard because of alternative winning lines that are still there but with allowed alternatives will certainly be easier. However their new easy nature should see them slip down the ratings.  The issue will be, is there enough legitimately hard problems to serve up problems at the equivalent rating without serving up duplicates?  If the answer is no then the set will get easier, but hopefully generating more legitimately difficult problems over time will remedy that.

Regards,
Richard.