Field enumeration is an interactive process between an enumerator and a respondent. It is prone to many sorts of non-sampling errors. Some of these errors may be related to the sex of the interviewer, errors occurring due to the presence of outsiders at the interview and to other factors. The "contamination effect" occurs when neighbours are present and are influenced by the survey topics and the responses given during the interview. Later, if they are interviewed, they will naturally be affected by the previous experience and their responses may be biased.
Another important error concerning the third persons is called the "presence of others effect". The presence of other persons during the interview will affect the responses given by the respondent, compared with interviews carried out in the absence of others.
The "response distortion" will vary according to different survey topics. For example, in some countries it has been found that in the presence of others, generally the current livestock is over-reported while the agricultural production is under-reported.
In order to avoid such errors occurring during the interviews, it is recommended that interviewers should be trained to insist that the interviews should not be carried out in the presence of others.
Depending on the topic of the survey and the specific questions, a sex bias may occur for both sexes, relating to the gender of all parties (respondent, interviewer, and other persons present) involved during the interview.
