Do Data Characteristics Change According to the Number of Scale Points Used? An Experiment Using 5-Point, 7-Point and 10-Point Scales

Abstract

This study examined how using Likert-type scales with either 5-point, 7-point or 10-point format affects the resultant data in terms of mean scores, and measures of dispersion and shape. Three groups of respondents were administered a series of eight questions (group n's = 300, 250, 185). Respondents were randomly selected members of the general public. A different scale format was administered to each group. The 5- and 7-point scales were rescaled to a comparable mean score out of ten. The study found that the 5- and 7-point scales produced the same mean score as each other, once they were rescaled. However, the 10-point format tended to produce slightly lower relative means than either the 5- or 7-point scales (after the latter were rescaled). The overall mean score of the eight questions was 0.3 scale points lower for the 10-point format compared to the rescaled 5- and 7-point formats. This difference was statistically significant at p = 0.04. In terms of the other data characteristics, there was very little difference among the scale formats in terms of variation about the mean, skewness or kurtosis. This study is 'good news' for research departments or agencies who ponder whether changing scale format will destroy the comparability of historical data. 5- and 7-point scales can easily be rescaled with the resultant data being quite comparable. In the case of comparing 5- or 7-point data to 10-point data, a straightforward rescaling and arithmetic adjustment easily facilitates the comparison. The study suggests that indicators of customer sentiment - such as satisfaction surveys - may be partially dependent on the choice of scale format. A 5- or 7-point scale is likely to produce slightly higher mean scores relative to the highest possible attainable score, compared to that produced from a 10-point scale. © 2008 The Market Research Society.