Parameterized Link Functions in Generalized Linear Random Effect Models: a Case Study on Breast Cancer Treatment

In non-linear random effects some attention has been very recently devoted to the analysis ofsuitable transformation of the response variables separately (Taylor 1996) or not (Oberg and Davidian 2000) from the transformations of the covariates and, as far as we know, no investigation has been carried out on the choice of link function in such models. In our study we consider the use of a random effect model when a parameterized family of links (Aranda-Ordaz 1981, Prentice 1996, Pregibon 1980, Stukel 1988 and Czado 1997) is introduced. We point out the advantages and the drawbacks associated with the choice of this data-driven kind of modeling. Difficulties in the interpretation of regression parameters, and therefore in understanding the influence of covariates, as well as problems related to loss of efficiency of estimates and overfitting, are discussed. A case study on radiotherapy usage in breast cancer treatment is discussed

The relationship between self-efficacy and health-related quality of life in Multiple Sclerosis patients

Background and Objectives Multiple sclerosis (MS) has a broad spectrum of physical, social, psychological effects and significant impact on quality of life (QoL). Several studies has showed the importance of self-efficacy as a predictor of QoL in patients with MS.This study aims at evaluating the robustness of the relationship between self-efficacy and QoL. Specifically it aims to test whether such relation will vanish under the following conditions: using a general measure of self-efficacy and controlling for level of impairment defined as a broad construct dealing with physical, social and working changes due to the illness condition. Methods One hundred-fifty five participants responded to a questionnaire, including QoL and general self-efficacy measures, socio demographic and clinical variables. Two nested structural equation models that differ for the presence or absence of the path connecting self-efficacy and QoL was estimated.Results and Conclusions The hypothesis of the vanishing of the relationship between self-efficacy and QoL had to be rejected. These results support the genuineness of this relation and emphasize the importance of interventions promoting self-efficacy to improve QoL in chronic diseases such as MS. From a methodological perspective this study is an example of the usefulness of formative indicators in QoL studies

Placing Multiple Tests on a Common Scale Using a Post-test Anchor Design: Effects of Item Position and Order on the Stability of Parameter Estimates

When there is an interest in tracking longitudinal trends of student educational achievement using standardized tests, the most common linking approach generally involves the inclusion of a common set of items across adjacent test administrations. However, this approach may not be feasible in the context of high-stakes testing due to undesirable exposure of administered items. In this paper, we propose an alternative design, which allows for the equating of multiple operational tests with no items in common based on the inclusion of common items in an anchor test administered in a post-test condition. We tested this approach using data from the assessment program implemented in Italy by the National Institute for the Educational Evaluation of Instruction and Training for the years 2010–2012, and from a convenience sample of 832 8th grade students. Additionally, we investigated the impact on functioning of common items of varying item position and orders across test forms. Linking of tests was performed using multiple-group Item Response Theory modeling. Results of linking indicated that operational tests showed little variation in difficulty over the years. Investigation of item position and order effects showed that changes in item position closer to the end of the test, as well as the positioning of difficult items at the beginning or in the middle section of a test lead to a significant increase in difficulty of common items. Overall, findings indicate that this approach represents a viable linking design, which can be useful when the inclusion of common items across operational tests is not possible. The impact of differential item functioning of common items on equating error and the ability to detect ability trends is discussed

Distractor Efficiency in an Item Pool for a Statistics Classroom Exam: Assessing Its Relation With Item Cognitive Level Classified According to Bloom’s Taxonomy

Multiple-choice items are one of the most commonly used tools for evaluating students’ knowledge and skills. A key aspect of this type of assessment is the presence of functioning distractors, i.e., incorrect alternatives intended to be plausible for students with lower achievement. To our knowledge, no work has investigated the relationship between distractor performance and the complexity of the cognitive task required to give the correct answer. The aim of this study was to investigate this relation, employing the first three levels of Bloom’s taxonomy (Knowledge, Comprehension, and Application). Specifically, it was hypothesized that items classified into a higher level of Bloom’s classification would show a greater number of functioning distractors. The study involved 174 items administered to a sample of 848 undergraduate psychology students during their statistics exam. Each student received 30 items randomly selected from the 174-item pool. The bivariate results mainly supported the authors’ hypothesis: the highest percentage of functioning distractors was observed among the items classified into the Application category (η2 = 0.024 and Phi = 0.25 for the dichotomized measure). When the analysis controlled for other item features, it lost statistical significance, partly because of the confounding effect of item difficulty