Scale construction utilising the Rasch unidimensional measurement model: A measurement of adolescent attitudes towards abortion

Abstract

Application of the Rasch model produced a valid and reliable scale measuring adolescent attitudes towards abortion, with stable measurement properties. The Rasch process provided an extensive range of diagnostic information concerning item and person fit, enabling changes to be made to scale items. This example shows the value of the Rasch model in developing scales for both social science and health disciplines.

First reported implementation of a German‐language progress test in an undergraduate dental curriculum: A prospective study

“…Generally, DPT items varied in difficulty within each of the 3 different tests; they fit to the trait distribution of the tested students and lay within a preferable range (Figures ) . Distribution of item difficulties was good for 3 out of 4 categories, with deviations only in “oral surgery,” with missing easy items in 1 test and lack of difficult items in another (Figures and ).…”

“…Generally, DPT items varied in difficulty within each of the 3 different tests; they fit to the trait distribution of the tested students and lay within a preferable range (Figures 3-5). 25,26 Distribution of item difficulties was good for 3 out of 4 categories, with deviations only in "oral surgery," with missing easy items in 1 test and lack of difficult items in another (Figures 4 and 5). The decision to split the item pool in groups of hundreds and administer 3 tests was made Therefore, and in contrast to established PTs, the difficulty parameters and the trait estimations between tests are not comparable.…”

Validation of the Dutch version of the Swallowing Quality-of-Life Questionnaire (DSWAL-QoL) and the adjusted DSWAL-QoL (aDSWAL-QoL) using item analysis with the Rasch model: a pilot study

“…In the cases of both the DSWAL-QoL and aDSWAL-QoL items, there are 5 response categories, resulting in 4 thresholds (= transitional points) [14]. Figure 1 represents a category probability curve in which the thresholds of a certain item are well ordered and form distinctive regions.…”

“…The CTT-psychometric assessment included an examination of internal consistency based on Cronbach’s alpha, test-retest reliability via the intraclass correlation coefficient (ICC), and/or construct validity based on principal component analysis (PCA) techniques [7, 11, 13]. Some drawbacks related to CTT methods are recognized [14, 15], such as test and sample dependence [14–16] and the assumption of equal weight for all of the items even if there is a difference in the level of difficulty [16]. The scale’s total sum score is based on ordinal values and the standard error of measurement is assumed to be constant [10, 15], in contrast to the Rasch methodology.…”

“…Item analysis using the Rasch model involves formal testing of a scale against a mathematic measurement model that specifies what should be expected in the item responses to provide interval-based measures instead of ordinal values [18, 19]. Interval measures are preferable to ordinal scales because they provide meaningful information about the relative differences and equivalences within the categories of the scale and enable the use of parametric statistics, which provide more powerful and precise results [14, 20]. If the observed data fit the model, the following can be concluded: interval data have been generated, the measurement scale demonstrates structural validity and objectivity, and the total score is statistically sufficient [17].…”