Research suggests that scale labels and scale points impact the statistical characteristics of response data and emphasize the importance of labeling all scale points. A scale with all points labeled effectively minimizes response bias, maximizes variance, maximizes power, and minimizes error. The results also suggest that variance may be maximized when the scale length is set at 7 points. Although researchers commonly believe using additional scale points will increase variance, results indicate increasing scale points beyond 7 does not increase variance. Taken together, a fully labeled, 7-point scale may provide the greatest benefits to researchers.
Source : Eutsler, J., & Lang, B. (2015). Rating scales in accounting research: The impact of scale points and labels. Behavioral Research in Accounting, 27(2), 35-51.
See the attached paper
