Then, the total of all Es are taken. Then, standard deviation of the project is calculated. The pilot project was for developing Ballistic Missiles and there have been thousands of contractors involved. This equals to the square root of the variance V. At the core, PERT is all about management probabilities.
Full directions come with all products. The back of the bottle has all the information you need. But remember, this is a natural supplement that does not carry the risk of side effects that medications do.