The aim of this field based work is to study in what measure different presentations of Likert-type items (including “continuous” options, i.e. marking the option on a straight line, with or without middle point and the use of all anchors vs extreme-only labels) induce different behaviours in items or scales distributions. In different areas of knowledge is necessary to know and explore indicators of attitude or motivation, in order to support the decision. To measure these non-measurable quantities, rating scales have been proposed, which intend to gather the “degree of affection” of an individual on a particular object or value. Several studies have evaluated and compared the behaviour of different rating scales. Some focus how to treat the items that compose the scales, others where the main goal is to analyse the scales' shape. As part of a wider project about perceptions of mathematics, four questionnaires were constructed: in the first two (A and B) the statements are evaluated by marking the response on a line segment (Visual Analogue Scale), labelled in the extreme and at the midpoint (A) or only at the extremes (B). In the third (C), Likert-type items with five labelled points are used (completely disagree, disagree, neither agree nor disagree, agree and totally agree), while in D only the extremes are labelled. We used theoretically-defined summated scales. The responses are compared at a scale level. The performance evaluation was made using location and shape measures, including robust variations.

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Likert-type items,Visual Analogue Scales (VAS),Robustness,Bootstrap confidence intervals