copy the linklink copied! Annex A. Relationship between the level of descriptors used in the Survey of Adult Skills (PIAAC) and other skills surveys
In presenting the results of the Survey of Adult Skills (PIAAC), the descriptors used to describe the characteristics of the tasks at each proficiency level in literacy and numeracy differ from those used when presenting the results of the International Adult Literacy Survey (IALS) and the Adult Literacy and Life Skills Survey (ALL). This is the result of:
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The introduction of the domain of literacy, which replaces the previously separate domains of prose and document literacy used in IALS and ALL.
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A change in the way in which the “proficiency” of individuals and the “difficulty” of items are defined in the Survey of Adult Skills compared to the IALS and ALL.
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A single literacy scale
The construct of “literacy” measured in the Survey of Adult Skills encompasses prose and document literacy, which were reported on separate scales in previous international adult literacy surveys, and also incorporates the reading of digital texts. Irrespective of any change to the definition of proficiency levels, the development of a new, single literacy scale necessitated a review of the descriptors of the proficiency levels used for reporting results.
The definition of proficiency levels
The Survey of Adult Skills locates items and individuals on the three proficiency scales using a response probability (RP) value of 0.67. In other words, individuals are located on the scale at the point at which he or she has a 67% probability of successfully completing a random set of items representing the construct measured. Items are located on the scale at the point at which they have a 67% probability of being successfully completed by a random sample of the adult population. This differs from the approach used in IALS and ALL in which a response probability of 0.80 was used. This change was made so that the approach used to define what it means for a person to be at a certain proficiency level was similar to that used in PISA (see OECD, 2010, p. 48).
The change in response probability has no consequences for either the estimation of the proficiency or the precision of the scales. The estimation of proficiency is independent of the selection of an RP value, as it is a function of the level of correct response to the test items. The precision of the scale is a function of the number of items in the scale, which is again independent of the choice of RP value. What the change in RP value does affect is the way proficiency is defined and described. In effect, “proficiency” is defined in terms of a different probability of successfully completing tasks. In the case of the shift from an RP value of 0.80 to one of 0.67, the result is that proficiency is described in terms of more difficult items that are completed with a lower probability of success.
This can be seen in the Table A.1 below, which presents item maps for literacy and numeracy when response probabilities of 0.67 and 0.80 are used. For example, the literacy item “Summer Streets” is located at 350 on the scale when a response probability of 0.67 is used as opposed to 369 when 0.80 is used. Similarly, the numeracy item “TV” moves from 279 to 260 when the response probability changes from 0.67 to 0.80.
As the score point ranges defining the proficiency levels for literacy and numeracy have not changed between IALS and ALL and the Survey of Adult Skills, the group of items used to describe each proficiency level – i.e. those that are located in the score-point range that defines a proficiency level – changes. This necessitated revising the descriptors of the proficiency levels. Tables A.3 and A.4 present the descriptors used in the Survey of Adult Skills and the previous surveys.
References
OECD (2010), PISA 2009 Results: What Students Know and Can Do: Student Performance in Reading, Mathematics and Science (Volume I), OECD Publishing, Paris, http://dx.doi.org/10.1787/9789264091450-en.
OECD/Statistics Canada (2011), Literacy for Life: Further Results from the Adult Literacy and Life Skills Survey, OECD Publishing, Paris, http://dx.doi.org/10.1787/9789264091269-en.
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