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The general topic of this Ph.D. thesis regards "Questionable Research Practices" (QRPs) and their effect on the replicability crisis in psychology and social sciences. QRPs are a set of bad research practices carried out to increase the likelihood of obtaining a significant result by providing some sort of manipulation of collected data. QRPs are related to the so-called replicability crisis, defined as the inability to replicate the results of an increasing number of studies. The proposed dissertation focuses on a specific form of QRPs named "Questionable Interim Analysis" (QIA). QIA implies that the data collection stopping rule depends on the previous interim analysis result. While the effect of this practice on the growth of false positive results is well known, its impact on the replicability of studies is still unclear. Furthermore, an objective tool to assess the incidence of this practice in a single study is, to our knowledge, still missing. In this project, we tried to overcome these limitations by evaluating the effects of QRPs on replication success and by proposing a formal tool to resize and control the QIA effects on statistical results. This document begins with a brief overview on the replicability crisis, QRPs, and the methods for identifying these practices in the literature (Chapter 1). Chapter 2 introduces a methodology to clarify the effect of some QRPs (cherry picking, questionable interim analyses, questionable inclusion of covariates, and questionable subgroup analyses) on replicability and determinates which replication success metric performs better in presence of these practices. The results show that the metric based on the golden sceptical p-value maintains low values of false positive replication success when QRPs are assumed. Chapter 3 presents a new probabilistic model to identify the incidence of QIA practice in the literature. It provides information about the larger or lower probability of this practice by estimating the ratio between the probability that a published result was obtained on the basis of a QIA practice or, alternatively, by a standard data collection approach. In Chapter 4, we show an application of the probabilistic models in the context of simulation studies. In particular, we illustrate how the new proposal improves some widely used simulation approaches to assess the false positive results in the context of QIA practices. Finally, in Chapter 5 the proposed models are discussed in terms of their utilities, limitations, and possible future extensions.

Le développement majeur de la thèse a été consacré au problème d’optimisation du choix de dose dans les essais de recherche de dose, en phase II. Nous avons considéré ce problème sous l’angle des fonctions d’utilité. Nous avons alloué une valeur d’utilité aux doses, le problème pour le sponsor étant de trouver la meilleure dose, c’est-à-dire celle dont l’utilité est la plus élevée.Dans ce travail, nous nous sommes limités à une seule fonction d’utilité, intégrant deux composantes: une composante liée à l’efficacité (la POS=puissance d’un essai de phase III de 1000 patients de cette dose contre placebo) et une autre liée à la safety. Pour cette dernière, nous avons choisi de la caractériser par la probabilité prédictive d’observer un taux de toxicité inférieur ou égal à un certain seuil (que nous avons fixé à 0.15) en phase III (toujours pour un essai de 1000 patients au total). Cette approche a l’avantage d’être similaire aux concepts utilisés dans les essais de phase I en oncologie qui ont notamment pour objectif la recherche de la dose liée à une toxicité limite (notion de ”Dose limiting Toxicity”).Nous avons retenu une approche bayésienne pour l’analyse des données de la phase II.Mis à part les avantages théoriques connus de l’approche bayésienne par rapport à l’approche fréquentiste (respect du principe de vraisemblance, dépendance moins grande aux résultats asymptotiques, robustesse), nous avons choisi l’approche bayésienne pour plusieurs raisons:• Combinant, par définition même de l’approche bayésienne, une information a priori avec les données disponibles, elle offre un cadre plus flexible la prise de décision du sponsor: lui permettant notamment d’intégrer de manière plus ou moins explicite les informations dont il dispose en dehors de l’essai de la phase II.• L’approche bayésienne autorise une plus grande flexibilité dans la formalisation des règles de décision.Nous avons étudié les propriétés des règles de décisions par simulation d’essais de phase II de différentes tailles: 250, 500 et 1000 patients. Pour ces deux derniers design nous avons aussi évalué l’intérêt de d’effectuer une analyse intermédiaire lorsque la moitié des patients a été enrôlée (c’est-à-dire avec respectivement les premiers 250 et 500 patients inclus). Le but était alors d’évaluer si, pour les essais de phase II de plus grande taille, s’autoriser la possibilité de choisir la dose au milieu de l’étude et de poursuivre l’étude jusqu’au bout si l’analyse intermédiaire n’est pas concluante permettait de réduire la taille de l’essai de phase II tout en préservant la pertinence du choix de dose final. / The main development of the thesis was devoted to the problem of dose choice optimization in dose-finding trials, in phase II. We have considered this problem from the perspective of utility functions. We have allocated a utility value to the doses itself, knowing that the sponsor’s problem was now to find the best dose, that is to say, the one having the highest utility. We have limited ourselves to a single utility function, integrating two components: an efficacy-related component (the PoS = the power of a phase III trial - with 1000 patients - of this dose versus placebo) and a safety-related component. For the latter, we chose to characterize it by the predictive probability of observing a toxicity rate lower or equal to a given threshold (that we set to 0.15) in phase III (still for a trial of 1000 patients in total). This approach has the advantage of being similar to the concepts used in phase I trials in Oncology, which particularly aim to find the dose related to a limiting toxicity (notion of "Dose limiting Toxicity").We have adopted a Bayesian approach for the analysis of phase II data. Apart from the known theoretical advantages of the Bayesian approach compared with the frequentist approach (respect of the likelihood principle, less dependency on asymptotic results, robustness), we chose this approach for several reasons:• It provides a more flexible framework for the decision-making of the sponsor because it offers the possibility to combine (by definition of the Bayesian approach) a priori information with the available data: in particular, it offers the possibility to integrate, more or less explicitly, the information available outside the phase II trial.• The Bayesian approach allows greater flexibility in the formalization of the decision rules.We studied the properties of decision rules by simulating phase II trials of different sizes: 250, 500 and 1000 patients. For the last two designs (500 and 1000 patients in phase II), we have also evaluated the interest of performing an interim analysis when half of the patients are enrolled (i.e. with the first 250and the first 500 patients included respectively). The purpose was then to evaluate whether or not, for larger phase II trials, allowing the possibility of choosing the dose in the middle of the study and continuing the study to the end if the interim analysis is not conclusive, could reduce the size of the phase II trial while preserving the relevance of the final dose choice.

This is an Action Research (AR) study with the senior phase Technology teachers at selected schools of Limpopo Province. The study was motivated by the fact that Technology Education is a foreign concept to many teachers and a new learning area in school curriculum both nationally and internationally. This was exacerbated by the many educational changes that took place in South Africa in the last 18 years. These changes include the overhauling of curriculum, which was the strategic and symbolic change since the first democratic election of 1994, but followed by its review. Thus, a new curriculum known as Curriculum 2005 (reviewed twice already) was developed in which Technology was introduced as a new subject. These changes drastically affected Technology Education and teachers’ coping demands on both the subject content and pedagogy escalated. In this study, AR, a strategy for a systematic, objective investigation with Technology teachers’ who are un- and under- qualified to teach Technology was considered. The study aimed at establishing intervention strategies to empower and emancipate senior phase Technology teachers in Mankweng Circuit from the said challenges above. Thus, the study sought to address the question: How could action research intervention be used to improve the teaching of senior phase Technology teachers who are un- and/or under-qualified? The intervention strategies were implemented through the AR cycles in spiral activities of planning, implementation and observation, action and reflection, whose principles were operationalized to develop participants from the situations that they face in their Technology teaching contexts. The study was designed from both critical theory perspective and participatory paradigm. The following instruments were used as a means to gather data: observations, interviews, questionnaires, field notes, video recording of lesson plans and logs of meetings. The study managed to come up with guidelines to develop and kick start AR with teachers. From the ii findings an AR model was developed to emancipate the un- and under-qualified Technology teachers. Themes from the challenges and AR were used to draft a six weeks plan to empower incapacitated Technology teachers. This investigation was shaped by the initial reflection or preliminary study conducted with the participants called reconnaissance study which revealed specific challenges that Technology teachers encountered daily in their classes. These challenges were turned into the themes, which together with the findings from the preliminary study and interview reflection per cycle were used to design the intervention strategies for the next main cycle. The findings of the study from both the preliminary investigation (presented in Chapter Two) and main AR (presented in Chapter Five) reveal an improvement in the teachers’ understanding and implementation of Technology – they were emancipated to a greater extent from the challenges prior to the AR intervention and post the AR intervention. It is true that coming together as AR co-researchers was the beginning of Technology teaching practice problem identification; keeping together was progressive in Technology teaching; but working together remains our success in Technology teaching then, now and in the future – post doctoral studies. / Curriculum and Instructional Studies / D. Ed. (Curriculum Studies)

This is an Action Research (AR) study with the senior phase Technology teachers at selected schools of Limpopo Province. The study was motivated by the fact that Technology Education is a foreign concept to many teachers and a new learning area in school curriculum both nationally and internationally. This was exacerbated by the many educational changes that took place in South Africa in the last 18 years. These changes include the overhauling of curriculum, which was the strategic and symbolic change since the first democratic election of 1994, but followed by its review. Thus, a new curriculum known as Curriculum 2005 (reviewed twice already) was developed in which Technology was introduced as a new subject. These changes drastically affected Technology Education and teachers’ coping demands on both the subject content and pedagogy escalated. In this study, AR, a strategy for a systematic, objective investigation with Technology teachers’ who are un- and under- qualified to teach Technology was considered. The study aimed at establishing intervention strategies to empower and emancipate senior phase Technology teachers in Mankweng Circuit from the said challenges above. Thus, the study sought to address the question: How could action research intervention be used to improve the teaching of senior phase Technology teachers who are un- and/or under-qualified? The intervention strategies were implemented through the AR cycles in spiral activities of planning, implementation and observation, action and reflection, whose principles were operationalized to develop participants from the situations that they face in their Technology teaching contexts. The study was designed from both critical theory perspective and participatory paradigm. The following instruments were used as a means to gather data: observations, interviews, questionnaires, field notes, video recording of lesson plans and logs of meetings. The study managed to come up with guidelines to develop and kick start AR with teachers. From the ii findings an AR model was developed to emancipate the un- and under-qualified Technology teachers. Themes from the challenges and AR were used to draft a six weeks plan to empower incapacitated Technology teachers. This investigation was shaped by the initial reflection or preliminary study conducted with the participants called reconnaissance study which revealed specific challenges that Technology teachers encountered daily in their classes. These challenges were turned into the themes, which together with the findings from the preliminary study and interview reflection per cycle were used to design the intervention strategies for the next main cycle. The findings of the study from both the preliminary investigation (presented in Chapter Two) and main AR (presented in Chapter Five) reveal an improvement in the teachers’ understanding and implementation of Technology – they were emancipated to a greater extent from the challenges prior to the AR intervention and post the AR intervention. It is true that coming together as AR co-researchers was the beginning of Technology teaching practice problem identification; keeping together was progressive in Technology teaching; but working together remains our success in Technology teaching then, now and in the future – post doctoral studies. / Curriculum and Instructional Studies / D. Ed. (Curriculum Studies)