• The activities are independent.
  
  
• The critical path contains a large no. of activities so that we can invoke the Central Limit Theorem.
  
  
• All activities not on the critical path are ignored.
  
  
• Activity times follow a Beta distribution.
  
  
• The mean and variance of the activities are given by (a+4m+b)/6 and [(b-a)/6]2.