When determining a schedule human factors should already be taken into account. I believe that a good project manager should already have sick days, and vacations accounted for. The most dangerous waste of resources would obviously be what cannot be accounted for, and was just previously mentioned, sick days. Vacations can be planned, and should be communicated to the PM in order to allow for proper accountability/planning. Sick days are the one variable that are never planned by the person taking them. I would count this as the largest and most detrimental human factor. Therefore, a good PM would go into the project plan fully knowing that a person, or persons, may fall ill which would push back the final delivery date of the project. To combat this the PM should be aware of the amount of possible sick days the company provides, and factor in how much a sick person would delay this project. Many project members have different talents and contribute at different rates. I would say one way to determine how much the project will be affected by this human error is to account for the best team member taking a work week off. Of course this factor will depend on team size, but in this example let’s just say a team of 5. With this sick time allocated, the project will be given a reasonable scope to be completed, and no one falls ill it should be completed before the expected time!