159 Target number of clusters 6 clusters of trend
units in 2015
main survey
9 clusters of new
units in 2015
main survey
105. Each student will be assigned one two-hour test form. A test form will be composed of four
clusters, with each cluster designed to occupy thirty minutes of testing time. The clusters are
placed in multiple computer
–based test forms, according to a rotated test design.
106. Each student will spend one hour on scientific literacy, with the remaining time assigned to
either one or two of the additional domains of reading, maths and collaborative problem solving.
For any countries taking the paper-based assessment instrument, intact clusters of 2006 units will
be formed into a number of test booklets. It is important to note that the paper-based assessment
will be limited to trend items and will not include any newly developed material. In contrast, the
computer-based instrument will include newly developed items as well as trend items. Care will be
taken when transposing paper-based trend items to an on-screen format that the presentation,
response format and cognitive demand remain comparable.
107. The desired balance between the three knowledge components, content, procedural and
epistemic knowledge, is shown in Figure 25 in terms of percentages of score points. Figure 26 also
shows the target distribution of score points among the various knowledge categories. These
weightings are broadly consistent with the previous framework and reflect a consensus view
amongst the experts consulted in the writing of this framework.
Figure 25. Target Distribution of Score Points for Knowledge Systems Knowledge types Physical Living Earth & Space Total over
