In cluster randomized trials (CRTs), groups are randomized to treatment arms rather than individuals while the outcome is assessed on the individuals within each cluster. Individuals within clusters tend to be more similar than in a randomly selected sample, which poses issues with dependence, which may lead to underestimated standard errors if ignored. To adjust for the correlation between individuals within clusters, two main approaches are used to analyze CRTs: cluster-level and individual-level analysis. In a cluster-level analysis summary measures are obtained for each cluster and then the two sets of cluster-specific measures are compared, such as with a t-test of the cluster means. A mixed model which takes into account cluster membership is an example of an individual-level analysis. We used a simulation study to quantify and compare power and bias of these two methods. We further take into account the effect of missing data. Complete datasets were generated and then data were deleted to simulate missing completely at random (MCAR) and missing at random (MAR) data. A balanced design, with two treatment groups and two time points was assumed. Cluster size, variance components (including within-subject, within-cluster and between-cluster variance) and proportion of missingness were varied to simulate common scenarios seen in practice. For each combination of parameters, 1,000 datasets were generated and analyzed. Results of our simulation study indicate that cluster-level analysis resulted in substantial loss of power when data were MAR. Individual-level analysis had higher power and remained unbiased, even with a small number of clusters.

The fossil population structure of the gastropod Neptunea angulata from the late Pliocene and Early Pleistocene was investigated in this project in order to contribute to a wider study on the influence of predation on populations and the evolutionary history of organisms. Over time, predator-prey relationships can drive evolution in a way similar to the Red Queen Hypothesis. However, before the effects of predation can be understood one must determine how the population dynamics functioned without the influence of predation. There are a number of problems that arise when determining population dynamics for fossil assemblages. These are usually caused by missing fossil data and the uncertain nature of their absence. Bias is rife within fossils at various stages from post-portem processes to when they are present in museum collections. One way to estimate these biases is to investigate the population structures of the fossils both directly from the fossil record and from museum collections. The variation in oxygen istopes found in N. angulata shells corresponded to yearly cycles which then were counted to determine the age of the specimen at time of death. Measuring the length of the spiral at yearly intervals provided the growth rate for the organism while it was alive. The growth rates were then used to determine the ages of specimens based on their size. The resulting ages were organized into an age distribution graph which was used to determine any museum bias. Bias in the preservation was also investigated by measuring the taphonomic damage of organisms of different size and then determine the distributions of size vs taphonomy. The ages of three specimens were found to differ even though the organisms had similar whorl lengths. As a result the growth equations differed and so different age distributions were calculated from each growth equation. All the age distributions demonstrated that the museum collections did show some bias against the smaller sized and thus younger specimens. There also appeared to be a size bias towards small N. angulata within the fossil record, with the extremely small individuals missing. The majority of the smallest specimens found in the field collections were not actually N. angulata specimens. A major problem with the results was a lack of data and a small sample size and it is highly recommended that an extensive collection and review of material be undertaken to fully determine the population structure present in the fossil assemblages. Other parts of the study, for example, the growth rates also require larger data sets in order for the confidence of the data to be improved. / I detta projekt studerades snäckpopulationer (Neptunea angulata) från Pliocen och Pleistocen för att besvara bredare frågeställningar om predation och dess inflytande på populationer och evolution. Innan man kan fastställa effekten av predation så behöver man förstå hur populationen betedde sig utan predationstryck. Flertalet problem uppstår när man studerar fossila populationer: tillgången på data kan vara begränsad och det kan vara svårt att se vad som saknas och varför. Information från fossil förloras från tiden som organismen dör fram till att de återfinns i museisamlingar. Ett sätt att uppskatta informationsförlusten är att studera fossil såväl i fossilbäddar som i museisamlingar. Genom att använda sig av den observerade cykliska skillnaden i stabila syreisotoper mellan olika tillväxtzoner i skalen av Neptunea angulata var det möjligt att uppskatta åldern på en organism vid en viss längd. Hastigheten med vilken snäckan växte beräknades genom att mäta förändringen i längd mellan olika åldrar. Genom att beräkna hur snabbt en snäcka växte så var det möjligt att använda storleken på fossilerna för att uppskatta dess ålder då den dog. Fossilen organiserades efter ålder för att visa populationsstrukturer. Förluster av fossil efter deposition uppskattades undersöktes genom att bestämma om mindre storleksgrupper var mer skadad än större storleksgrupper . Den varierade tillväxten hos olika snäckor användes för att beräkna dess åldrar. Det upptäcktes att museisamlingar tenderade att inneha större och äldre individer. Det tycktes också finnas färre små fossil av Neptunea angulata inom opartisk samling. Några av de extrement små individerna saknades helt och majoriteten av de minsta fossilen var inte ens Neptunea angulata. Skador på fossilen var större ju mindre individerna var. Mängden data inverkade negativt på denna studie och därför rekommenderas en omfattande genomgång av de tillgängliga samlingarna för att bättre kunna besvara frågor kring denna population i framtiden.

The Swedish Curriculum for the upper secondary school states that teachers should “ensure that teaching in terms of content and its organisation is typified by a gender perspective” (Skolverket 2011, p. 9). Considering that there is no further information regarding what a “gender perspective” means in reality, this sentence could be interpreted in many different ways. This study aims to explore how EFL teachers deal with linguistic gender equality, and which strategies they use to maintain a gender inclusive language in their classroom. Six interviews were conducted with EFL teachers at upper secondary schools in Stockholm, Sweden. The results indicated that the teachers thought this was an important issue to consider in teaching, andthat they had well-reasoned strategies for maintaining a gender perspective. The most prominently discussed strategies were encouraging reflection and discussion on these matters, and choosing appropriate literature that either would show a variety of different perspectives, or else would question the social norm. However, concerning their own language production, some of the teachers lacked explicit strategies for maintaining a gender inclusive language, which could derive from a lack in knowledge. Thus, this essay proposes that gender inequality in language needs to be more explicitly explored, both in teacher education and in further education for employed teachers. The teachers displayed an ambition to maintain a gender equal language teaching; and would benefit from more explicit tools to realize that.

In this thesis, we propose a circuit design technique that reduces the energy utilized by any logic circuit for computation. We achieve this, by reducing the voltage swing on the circuit without greatly compromising the speed of operation and keeping in mind the noise margin constraints. Our technique involves the use of head or tail transistors that provide a Vth drop in the voltage swing. We choose to use head or tail transistors on alternate logic levels providing us with an option of driver stage, based on the noise margin of the subsequent stage. We demonstrate the working of this concept on inverter chains, to prove the correctness as well as the ability of the reduced voltage swing circuits to drive subsequent stages. We also discuss the implementation of this technique on basic gates and simple combinational circuits. We then show detailed experiments on a larger circuit, in this case a Kogge-Stone parallel prefix adder. We will discuss the overheads involved in the design and methods to partially overcome these by the use of selectively skewed gates and application of forward body bias. Finally we implement the same design using a different technology to demonstrate the scalability of the technique. / text

A loan deal is often composed of several components (for example, a 3-year revolving loan, a 10-year secured senior term loan, and a 5-year subordinated term loan). The division of a deal into two or more components, each with different risk characteristics, is called tranching. This study recognizes the importance of tranching and establishes tranching as an integral component of a syndicated loan structure. In the first essay, we present a model to explain the economic value of tranching and show that riskier firms are more likely to take loans with multiple tranches. Therefore, the average credit spread on syndicated loans with multiple tranches is higher than that on nontranched loans. However, after accounting for the risk characteristics of a tranched loan, we show that a given tranche of a multi-tranche loan, on average, has a lower credit spread than an otherwise similar loan that is not part of a multi-tranche loan. We also show that the benefits of tranching accrue primarily to borrowers with speculative debt ratings. Prior studies have found an abnormal stock return of 100 to 150 basis points for firms that announce they have borrowed funds from a bank. Despite some conflicting evidence (Peterson and Rajan, 2002; Thomas and Wang, 2004; Billett, Flannery and Garfinkel, 2006), the literature tends to interpret this positive bank loan announcement effect as the markets response to the mitigation of information asymmetry regarding the borrowing firm caused by the certification role of the lending banks who act as quasi-insiders. In the second essay, we document that a strong selection bias exists in prior studies. We show that less than a quarter of the loans made by banks are ever announced by borrowing firms and the loans that are announced are systematically different from loans that are never announced by the firms. Firms with low debt ratings, firms with zero or negative profits but positive interest expense, firms that take large loans in relation to their assets base, firms with little analyst following, and firms with high forecasted EPS growth are more likely to announce their loans. We show that while there was a positive announcement effect over the period 1987 to 1995, loan announcements elicited zero or negative returns in the last ten years as the mix of companies announcing loans changed over time.

Learning and experience shape mate preferences in many species. My thesis investigates the role of experience on mating behavior of male and female sailfin mollies (Poecilia latipinna). In the first chapter I explore whether adult experience influences male sailfin molly mate preference for their sexual parasite, the Amazon molly (Poecilia formosa), and whether experience could account for reproductive character displacement (RCD) of male mate preference in this species. Sailfin males from sympatric populations show a stronger preference for conspecific females over Amazon mollies than do males from allopatric populations. I exposed males from sympatric and allopatric populations to either a sailfin female or an Amazon prior to a mating trial with an Amazon. For the allopatric population, males with recent experience with an Amazon directed fewer mating behaviors towards an Amazon during mating trials than did males with recent experience with a sailfin. Males from the sympatric population, however, performed the same amount of mating behaviors towards an Amazon regardless of experience. Thus adult experience influences mating preferences and suggests that experience may play a role in RCD in this species. In the second chapter I investigate whether a learned sensory bias could influence female mate preferences. Sensory biases that influence mate preferences can arise through selection on the sensory system in foraging and predator detection domains. I tested whether a learned preference originating outside of the mating domain, specifically a color-based food preference, can be transferred to a color-based preference for a male trait. I trained female sailfin mollies to associate either green or blue with food and then tested their preference for animated male sailfins featuring either a blue or green spot. I found that females did not prefer the male with the same color spot to which they had been conditioned. I discuss the problem of learned preference transfer and suggest directions for future research into the role of learning in sensory bias. / text

Older adults have been reported to show attentional preference for positive stimuli and attentional avoidance from negative stimuli. The relationship between this pattern of emotional attention and emotion regulation, however, is not well known. The present study aims to replicate the findings of age-related attentional bias for emotional stimuli and investigate the potential relationship between biased attention and emotion regulation/dysregulation in Chinese older adults. 46 older adults and 46 younger adults participated in an attention task, which measured their reaction time towards negative and neutral facial stimuli, and a questionnaire survey, which elicited self-reports of their levels of emotion regulation and dysregulation. Results showed that there was a biased attention for negative faces in older adults, but not in younger adults. There were also differences between emotion regulation/dysregulation measures in the two age groups. When associating the attentional bias score with the emotion dysregulation measures, significant correlations were found between biased attention and overall difficulty in emotion regulation and lack of emotional clarity. The data supported the age-related bias of emotional attention, and revealed potential relationship between biased attention and emotion regulation in older adults. / published_or_final_version / Clinical Psychology / Master / Master of Social Sciences

This study investigated bias at the item level in six subtests of the California Achievement Tests (CAT). Variability of performance across all individual items of the CAT for fourth graders from three ethnic groups was examined. A two-factor (item scores and ethnicity) ANOVA procedure was used to examine the interaction between Anglo and Hispanic children and between Anglo and black subjects on individual test items of the subtests. Significant F-ratios for the Items x Groups interaction were further examined by using Bonerroni's post-hoc test for the purpose of identifying specific items reflecting cultural bias. A total of twenty-one items was identified as culturally biased. Of these items, sixteen were biased against Hispanics, three items were found to contain bias against blacks, and two items reflected bias against both Hispanic and black children. Of these twenty-one items identified as biased, eighteen belonged to four verbal subtests and three items are part of the two mathematics subtests. In addition to these items identified as being statistically biased, this study suggests that ethnocultural differences exist on overall performance levels between groups. For example, on the verbal subtests, there was a total of only three items on which Hispanic children scored higher than Anglo subjects, and only one item which reflected a better performance by black children than Anglo students. Higher performance levels by Anglo subjects were also noted on mathematic subtests, wherein Hispanic children scored higher on six items than their Anglo counterparts, and black subjects outperformed Anglo children on only one item. These data reflected a tendency of higher performance by Anglo students across all subtests when by an examination of the number of items passed or failed by members of each ethnic group was made. The examination of the verbal subtests additionally showed that Anglos passed sixty-five items, Hispanic children passed twenty-four items and thirty-two items were passed by black subjects. This trend continued on the mathematics subtests, where thirty-one items were passed by Anglo students and seventeen and fifteen items were passed by Hispanic and black children respectively. The findings of this study led to the conclusion that the majority of items on the CAT does not reflect evidence of cultural bias. There were, however, a limited number of items on which either Hispanic or black children out-performed their Anglo counterparts. Implications of these findings were discussed and recommendations were made for future studies to examine bias at the item level.

The purpose of this study was to investigate bias in the areas of examiner disability, and examiner and examinee gender on test scores of selected subtests of the WAIS-R. The subjects of this study were 101 nondisabled University of Arizona Introductory Psychology students who were randomly assigned to treatment and control groups. The treatment group was administered the Arithmetic and Picture Completion subtests of the WAIS-R by a wheelchair bound examiner (a nondisabled examiner posing as a disabled examiner). The control group was administered the same subtests by a nonwheelchair bound examiner. The data were analyzed by two three-way ANOVAs. The three-way analysis of variance tested for significant relationships between main effects of the three independent variables--examiner disability, examiner gender and examinee gender, and the scores of the arthmetic and Picture Completion subtests, and also for two-way and three-way interactive effects of the three variables and the subtest scores. Results indicated that in terms of bias operating to influence the individually administered subtest scores, only examinee gender was found to have a significant effect, with subtest scores for male examinees significantly higher than those for female examinees, on both Arithmetic and Picture Completion subtests. Nonsignificant relationships were found between the other two independent variables of examiner disability and examiner gender, and subtest scores. The presence of a visible, physical disability on the part of the examiner, and the gender of the examiner were not seen to be operating as bias, and were not seen to be impacting on subtest scores. Due to limitations of the study that included instrumentation, interaction of testing and treatment, interaction of selection and treatment, reactive arrangements and history, and due to lack of supportive research in the area of examinee gender as bias influencing test scores, the findings of this study need to be interpreted with caution, and should be considered speculative at best.

近年來，媒體偏頗（media bias）的現象愈來愈引起經濟學家的注意。本文指出，即便媒體本身的意識型態中立，他們仍然有誘因為了迎合閱聽眾的口味而帶著立場扭曲他們的報導。比較有趣的是，在這篇文章中，即使沒有在文獻中提到的價格競爭或是媒體考量本身聲譽的效果，在一些普遍的情況下，新聞媒體的意識型態仍會傾向兩極化。另外，我們也指出，這樣的兩極化現象，會透過媒體與閱聽眾之間的交互影響輕易地深化。 / Media bias has been attracting more and more attention of economists in recent years. This essay shows that, even the media firms are ideologically neutral, they still have incentives to slant their news to cater to the audience or readers. An interesting feature of this paper is that, even though without reputation and price competition effects proposed in the literature, the ideology of news reported is apt to be polarized under some situations which are very common in reality. We also show that polarization could be easily deepened through some interaction between media firms and news consumers.