You can find a ceiling effect with the two dose trial if there is one. What you can't find is the specific level at which it occurs. Not the same thing as you posted.
In Rett we already know that 5 mg has a easily measurable effect. If the 30 mg dose shows increased efficacy and the 50 mg dose also shows an increase over 30mg, then there is not likely to be a ceiling effect or it happens between 30 and 50 mg.
If the 50 mg dose does not show an increase in efficacy then there is a ceiling effect between 5mg an 30 mg.
The point is that there is information that can be obtained if such an effect exists.
Market Data 
Markets 
AI
