Experimental Design

In response to the series of posts on my research into predictive factors for sires' offsprings' earnings per start, 'Winston...not really' suggested the basic design for an experiment involving breeding multiple stallions to the same band of mares to avoid the possibility that what we're measuring when look at stallion performance is simply a result of a systematic difference in the quality of mares that are being sent to them. His suggestion is definitely a good idea...if you have a few billion dollars to spare. For anyone who doesn't, statistical analysis should be sufficient. I've mentioned before that we're going to need to make adjustments to the sire statistics to take the quality of mares into account, and its something I'd like to tackle in the near future. However, if we're going to adjust for 'quality' of mare, it may make sense to at how to measure that quality first. Racing success? Previous breeding success? Quality of bloodlines? I know that some studies on the topic have indicated that racing success is more important than bloodlines, but I'm not sure anyone has tried to measure the relative predictive value of racing success versus success of previous progency...and how the balance changes as a mare ages and we're able to gather data on a slightly larger number of her progeny.