It is intended that the manual be used to its fullest extent. However, its employment will be conditioned by several practical factors. The first and most important is the time element. The absolute amount of time available to the different operators by whom these techniques may be employed if often drastically limited. In most cases it will probably be sufficient if the operator is conscious and conversant with the techniques, without employing, in his work situation, more than a limited number of those that appear most useful to him.
Every operator can assign priorities to the techniques.
Some are more important than others. Moreover, some are easier to employ and better known than others and require less work to put them into effect. Limitations of personnel will also condition the full use of the manual. Where an evaluation officer is not assigned to a country mission and where a single officer may occupy two positions or suffer great demands upon his time, without staff to assist him, his use of the manual will be almost entirely intellectual and internal, with perhaps no more than an hour a week devoted to the conscious implementation of the methods outlined herein. Under some circumstances, too, local research resources are so poor as to limit exceedingly the number of techniques that can be put into effect, even over a considerable period of time.