Denver,
Harry, I know what a double blind study is, but can we assume that there is one person receiving the placebo for every person receiving the actual drug? If that is the case then when they report that a study revealed that 500 patients receiving a new drug experienced certain results, can we assume that there were 1000 participants (500 who got the drug and 500 who got the placebo)?
I'm not asking for any particular reason, just curious.
It all depends on the design of the study. Some studies have 50% on the drug and 50% on placebo (I believe the Tysabri Phase III trials did this) and others have different numbers. For instance, when my wife took part in a trial a number of years ago, they had one patient on the high dose of the drug, one on the medium dose, one on the low dose and one on the placebo. So you had a one in four chance of being on the placebo.
If you are able to get your hands on the actual study or a detailed abstract, the breakdown will be given very clearly.
The design of a study takes a lot of work and there are many variables that have to be carefully outlined. This design can effect the outcome so that's why it is so important to read the studies to determine just what happened. It is quite an art.
Harry