CPM is activity oriented i.e. CPM network is built on the basis of activities.
CPM is a deterministic model i.e. it does not take into account the uncertainties involved in the estimation of time for execution of a job or an activity.

Work study consists of two techniques namely method study and work measurement.
The method study is a technique to simplify the job and develop more economical methods of doing it.
The Work measurement is concerned with the elimination of ineffective time and establishment of time standards for a job.
Work study is mainly aimed at determining the most efficient method of performing a job. Basic tool in work study is stop watch.