copy the linklink copied! Differences in test administration and construct coverage

Over the past decades, digital technologies have fundamentally transformed the ways we read and manage information. Digital technologies are also transforming teaching and learning, and how schools assess students. To reflect how students and societies now commonly access, use and communicate information, starting with the 2015 assessment cycle, the PISA test was delivered mainly on computers. Existing tasks were adapted for delivery on screen; new tasks (initially only in science, then, for PISA 2018, also in reading) were developed that made use of the affordances of computer-based testing and that reflected the new situations in which students apply their science or reading skills in real life.

Because pen-and-paper tests are composed only of items initially developed for cycles up to PISA 2012, the paper-based version of the PISA 2018 test does not reflect the updates made to the assessment frameworks and to the instruments for science and reading. In contrast, the paper-based instruments for mathematics and their corresponding computer-based versions have their roots in the same framework, originally developed for PISA 2012.

The changes introduced in the assessment of science, in 2015, and of reading, in 2018, have deep implications for the set of assessment tasks used. The new frameworks resulted in a larger amount of assessment tasks at all levels; extended coverage of the reading and science scales through tasks that assess basic reading processes and emerging science skills (proficiency Levels 1b in science and 1c in reading); an expanded range of skills measured by PISA; and the inclusion of new processes or new situations in which students’ competence manifests itself. Table I.A5.1 summarises the differences between the paper- and computer-based tests of reading; Table I.A5.2 summarises the corresponding differences in science.2

In reading, newly developed tasks could include using hyperlinks or other navigation tools (e.g. menus, scroll bars) to move between text segments. At the beginning of the reading test, a section was added to measure reading fluency, using timed sentence-comprehension tasks (see Chapter 1, Annex A6 and Annex C). None of these tasks would be feasible in a large-scale paper-based assessment. In science, new “interactive” tasks were developed for the PISA 2015 assessment. These tasks used computer simulations to assess students’ ability to conduct scientific enquiry and interpret the resulting evidence. In these tasks, the information that students see on the screen is determined, in part, by their own interactions (through mouse clicks, keyboard strokes, etc.) with the task.

There are other differences between the PISA paper- and computer-based tests in addition to the tasks included in the tests and the medium through which students interacted with those tasks.

While the total testing time for all students was two hours, students who sat the test using computers had to take a break before starting work on the second half of the test, and had to wait until the end of the first hour before doing so. Students who sat the paper-based test also had to take a break after one hour of testing, but they could start working on the second half of the test during that first hour.

Another difference in test administration was that students who sat the test using computers could not go back to questions in a previous test unit or revise their answers during the test or after reaching the end of the test sequence (neither at the end of the first hour, nor at the end of the second hour).3 In contrast, students who sat the paper-based version could, if they finished earlier, return to their unsolved tasks or change the answers they had originally given to some of the questions.

In 2018, and on average across countries that delivered the test on computer, 50 % of students completed the reading test within about 40 minutes, i.e. about 20 minutes before the end of the test hour (Table I.A8.15). For additional analyses on response-time data, see Annex A8 and in the PISA 2018 Technical Report (OECD, forthcoming_[1]).

In addition, the computer-based test in reading was a multi-stage adaptive test (see Chapter 1). In practice, the test forms consisted of three segments (stages): students were presented with a particular sequence of test tasks in the second and third stages based on a stochastic algorithm that took into account their performance on previous segments (OECD, forthcoming_[1]; Yamamoto, Shin and Khorramdel, 2018_[2]).4 In science and mathematics (and also in reading for those countries that delivered the paper-based test), students were assigned test forms via a random draw, independent of the student’s proficiency or behaviour on the test.

copy the linklink copied! How the evidence about mode effects was used to link the two delivery formats

In order to ensure comparability of results between the computer-delivered tasks and the paper-based tasks that were used in previous PISA assessments (and are still in use in countries that use paper instruments), for the test items common to the two administration modes, the invariance of item characteristics was investigated using statistical procedures. These included model-fit indices to identify measurement invariance (see Annex A6), and a randomised mode-effect study in the PISA 2015 field trial that compared students’ responses to paper-based and computer-delivered versions of the same tasks across equivalent international samples (OECD, 2016_[3]). For the majority of items, the results supported the use of common difficulty and discrimination parameters across the two modes of assessment. For some items, however, the computer-delivered version was found to have a different relationship with student proficiency from the corresponding, original paper version. Such tasks had different difficulty parameters (and sometimes different discrimination parameters) in countries that delivered the test on computer. In effect, this partial invariance approach both accounts for and corrects the potential effect of mode differences on test scores.

Table I.A5.3 shows the number of anchor items that support the reporting of results from the computer-based and paper-based assessments on a common scale. The large number of items with common difficulty and discrimination parameters indicates a strong link between the scales. This strong link corroborates the validity of mean comparisons across countries that delivered the test in different modes. At the same time, Table I.A5.3 also shows that a large number of items used in the PISA 2018 computer-based tests of reading and, to a lesser extent, science, were not delivered on paper. Caution is therefore required when drawing conclusions about the meaning of scale scores from paper-based tests, when the evidence that supports these conclusions is based on the full set of items. For example, the proficiency of students who sat the PISA 2018 paper-based test of reading should be described in terms of the PISA 2009 proficiency levels, not the PISA 2018 proficiency levels, and similarly for science. This means, for example, that even though PISA 2018 developed a description of the skills of students who scored below Level 1b in reading, it remains unclear whether students who scored within the range of Level 1c on the paper-based tests have acquired these basic reading skills.