Decision Criteria

Interim Success

Interim Futility

Final Success

Final Futility


Pr(R_{ED90} –Ctrl > 0)

>95%

<20%
  
Pr(R_{ED90} –Ctrl > 0.95)

>70%
   
Pr(Rd_{max} –Ctrl > 0) > 0.95 and Pr(R_{ED90} –Ctrl > 0) >95%
  
Yes

No

 Pr(R_{ED90} –Ctrl > 0): The probability of dose response near ED90 dose level achieves a drug effect greater than the control or placebo
 Pr(R_{ED90} –Ctrl > 0.95): The probability of dose response near ED90 dose level achieves a drug effect greater than the control or placebo and 0.95 is the clinical significant difference
 Pr(Rd_{max} –Ctrl > 0): The probability of any dose with maximal effect achieves a drug effect greater than the control or placebo
 Only final success and futility are accessed in fixed design