A unipolar scale is an ordinal scale worded around one “pole.” For example, a 5-point rating scale of “not at all likely, slightly likely, somewhat likely, very likely, and extremely likely” is unipolar. With this alternate wording, the scale would be bipolar: “Extremely unlikely, slightly unlikely, neutral, very likely, and extremely likely.” Some researchers prefer unipolar scales as they may be simpler for the respondent. Other researchers favor bipolar scales because the “ends” are more distinct. Research studies have found that using unipolar and bipolar scales impacts survey responses (see this article for one such study).
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