what does the pi signify in statistics? I have a Ho and Ha. pi(infested)= pi(control) Solution pi in statistics in this context means that is a proportion that you can calculate with a sample For example: lets say that the sample is N= 50 in this sample there are 20 person infested and there are 30 person in control p for infested is the proportion of persons that are infested of a sample of 50 and is 20/50=0.4 p for control is the proportion of persons that are in control of a sample of 50 and is 30/50=0.6.