Under this method enumerators shall select the respondents in place of those not available, as per the quota fixed according to guide lines provided to them. This latitude to the enumerators especially in rural areas for some marketing studies help in completing the work in the time assigned. Sometimes some reserve units are also pre determined and alternative choice would be to elect substitutes units out of the reserve units.
This method enables enables the completion of investigation in time since no time is lost in consulting the higher authorities and awaiting for their instructions.
If the properly trained staff is not employed, it will distort the basis objective of the study since the interviewers may taken latitude in replacing the items according to their own whims.