Once the project has begun it is important to monitor its progress and modify the plans. Estimation is the honest prediction of what is likely to happen. Estimates with well understood assumptions can be useful in the identification and control of risks of unachievable targets. Targets that are very pessimistic can give slack that can be used for reducing risks or coping with the effect of problems. However targets that ignore estimates may be unachievable.
Good scheduling reduces the percentage of tasks on the critical path.
It includes response plans for use to mitigate risks. Poor planning can exaggerate the risks from poor estimation, target-setting, resource planning, quality planning and risk management. A lack of critical path analysis can mean that existing risks are much worse than expected. Good resource planning involves the timely allocation of sufficient and suitable staff to the work - and to do this without having periods of inactivity. However a lack of effective resource planning can result in delayed starts to tasks while the people wait for staff to finish other work.