Of course the questioning procedure is itself an artificial product, and any of a number of factors including questionnaire design, questioning method, sampling and analysis may play a part in influencing the outcome of the poll. It's near impossible to come up with a faultless methodology.
另外就是問卷畢竟是個人為的過程，包括問卷設計、問問題的方法、抽樣、分析等，每一環的操作都有可能影響到問卷的結果，這在方法上很難達到盡善盡美。