I recently re-ran a survey for year to year comparisons. In the recent survey I changed the Likert scale slightly by anchoring each box rather than just # 1 and # 6.
In other words, my scale went from this:
1 – agree completely, 2 , 3 , 4 , 5 , 6 – disagree completely
To this:
1 – agree completely
2 – agree
3 – somewhat agree
4 – somewhat disagree
5 – disagree
6 – disagree completely
Will the year to year comparisons still be accurate? I have looked online but have not found any standard best practices in this area. Thanks.
Best Answer
I think there are some studies claiming that it makes a difference regarding the distribution of responses. The main concern is to justify the interval scale. Likert scales anchor every point and try to encourage equal interval sizes. Strictly speaking, a Likert scale always requires that all points are anchored.
However, I doubt it makes a difference. Whatever anchoring you use, data will always be subject to scale usage heterogeneity (http://www.jstor.org/stable/2670337). This effect will be much stronger than any effect caused by anchoring.