In recent years, a virtual library of medical research has concluded that, other factors being equal, complex surgery turns out better when it's done at hospitals where the procedure is done a lot.

VOA: standard.2010.07.14

The paper's authors tried to take into account other factors, but they admit it may not have been entirely possible to quantify differences in, for example,the recipient's health, which can be a big factor in the success of a transplant.

VOA: standard.2010.07.14

That's an excellent question, especially looking into factors that affect the return-generating process in the stock market-in other words, factors that affect the stock prices in a conventional sense: Market liquidity, length of the daily fasting period, especially contrasting summer months with winter months when Ramadan coincides with one versus the other, with the length of day being really longer during summer months.

VOA: standard.2010.08.05