a) Availability of the other helping social health structures like hospitals, health oriented activity groups, health facilities, churches, playgrounds and voluntary organizations facilitate in applying intervention and also in monitoring and evaluation.

b) Positive preventive climate, if available, is very much beneficial and if not available, it has to be created by means of prior community sensitization.

c) the need for the trial must be felt by the community as a dire necessity e.g. any public health problem causing high morbidity, mortality or disability as community participation will be maximum in those circumstances, even though this factor may lead to bias during the sampling for the study.

d) Practical feasibility, financial and time constraints are to be met prior to the commencement of the trial.