# Impact of Computer-Based Assessments on the Science's Ranks of Secondary Students
## 2 Assessments and CBAs
### Advantages and Risks of Using CBAs  
The quality of tests and of testing instruments should be primarily compared in terms of their degree of validity, reliability, and fairness, particularly when they are used for summative or high-stakes purposes. From the view of the TAM model, to understand the benefits and risks of adopting CBAs, it is important to check how well digital exams deal with these factors in comparison with traditional PBAs. Validity is the \"sine qua non\" of assessment. Without evidence of validity, assessments in education have little or no intrinsic meaning [21]. Among the notions of validity, \"Construct validity\" is the most important as it is an essential measure of the perceived overall validity of a test. [PERSON] and [PERSON] (1955) defined construct as \"some postulated attribute of people, assumed to be reflected in test performance (p. 283) [22]\". In simpler words, \"construct validity\" broadly refers to whether a test measures what it claims to measure. An alleged advantage of CBAs is that they would allow measuring _new_ constructs (e.g., solving complex scientific problems interacting with a simulator in real-time), which do not fit well or are not possible with traditional PBAs [23; 24; 25]. For example, the chance to insert dynamic stimuli, such as multimedia files or interactive objects into digital items, would tend to increase the level of \"construct representations [26]\". Therefore, if we assume that \"The best construct is the one around which we can build the greatest number of inferences (p. 288) [22]\", CBAs would offer more advantages and capacity than PBAs to draw advanced inferences. In short, to assess better. To illustrate this argument, it is worth mentioning the effort invested within PISA and TIMSS to develop in each cycle innovative interactive instruments to measure abilities which \"_have never been tested before_\" [27; 28]. Besides of valid, tests must also be reliable and fair [9]. Test fairness basically refers to provide equal opportunities to all test-takers [29], and test reliability refers to the degree to which an assessment tool produces stable and consistent results under similar circumstances and, thus, yield accurate test scores [30]. It is known that human scoring, besides being labor intensive and time-consuming, is also prone to validity and reliability problems [31]. Therefore, another double advantage of using automatically marked CBAs would be that they are free of common human-marking biases [32; 33] and that machine's scores are more accurate than the teacher's scores [34]. Most of the risks and threats of shifting to CBAs stem from the old concern that \"computers affect testing\" [35] and the subsequent risk of \"_measuring other skills different from those intended, as for example the student's skills to use technological devices_\" [36]. For more than a decade, the lack of familiarity with electronic devices was the main threat reported in literature to question the validity and fairness of CBAs. However, a very recent work did not find evidence that computer access or familiarity was nowadays more important for taking digital- than for taking paper-based tests [37]. Current discussions about the validity of CBAs are more centered on other issues, as for example, the impact of unappropriated designs of the multimedia and interactive elements embedded in digital items [5] or about how to ensure secure administrations of CBAs. These risks might lead to false positives (i.e., when CBAs help test-takers more than expected) or to false negatives (i.e., when multimedia contents induce unexpected \"noise\" causing wrong answers) outcomes. On another hand, a remarkable advantage of CBAs is the capacity to make a systematic capture of log data during the assessment experience. Conveniently analyzed, these data could provide new valuable insights.