43.行銷資訊的蒐集可透過不同方式來接觸受訪者，其中最具彈性、可蒐集資訊量多，但訪員影響的控 制(controlofinterviewereffects)較差的是何種接觸方式？
(A)郵寄問卷
(B)電話訪問
(C)人員訪談
(D)觀察研究

調訪者效應 (Interviewer Effect)

The interviewer effect (also called interviewer variance or interviewer error) is the distortion of response to a personal or telephone interview which results from differential reactions to the social style and personality of interviewers or to their presentation of particular questions. The use of fixed-wording questions is one method of reducing interviewer bias. Anthropological research and case-studies are also affected by the problem, which is exacerbated by the self-fulfilling prophecy, when the researcher is also the interviewer it is also any effect on data gathered from interviewing people that is caused by the behavior or characteristics (real or perceived) of the interviewer.
訪調員效應（也稱為訪調員方差或訪調員錯誤）是指由於訪調員的社會風格或個性差異，或對特定問題的反應而導致的對個人或電話採訪的反應的扭曲。使用固定措辭的問題是她減少面試官偏見的一種方法。
- 來源 維基百科 

所以只要有人與人交談的情況下都應該會造成有主觀偏見吧？就算是電話訪問，也會因為對方的語氣、音調等等對這個人造成有主觀意見。B/C 都是正解吧