Optimum sample size allocation to minimize cost or maximize power for the two‐sample trimmed mean test

When planning a study, sample size determination is one of the most important tasks facing the researcher. The size will depend on the purpose of the study, the cost limitations, and the nature of the data. By specifying the standard deviation ratio and/or the sample size ratio, the present study considers the problem of heterogeneous variances and non‐normality for Yuen's two‐group test and develops sample size formulas to minimize the total cost or maximize the power of the test. For a given power, the sample size allocation ratio can be manipulated so that the proposed formulas can minimize the total cost, the total sample size, or the sum of total sample size and total cost. On the other hand, for a given total cost, the optimum sample size allocation ratio can maximize the statistical power of the test. After the sample size is determined, the present simulation applies Yuen's test to the sample generated, and then the procedure is validated in terms of Type I errors and power. Simulation results show that the proposed formulas can control Type I errors and achieve the desired power under the various conditions specified. Finally, the implications for determining sample sizes in experimental studies and future research are discussed.     

The maximum priority index method for severely constrained item selection in computerized adaptive testing

This paper introduces a new heuristic approach, the maximum priority index (MPI) method, for severely constrained item selection in computerized adaptive testing. Our simulation study shows that it is able to accommodate various non‐statistical constraints simultaneously, such as content balancing, exposure control, answer key balancing, and so on. Compared with the weighted deviation modelling method, it leads to fewer constraint violations and better exposure control while maintaining the same level of measurement precision.     

An effect size index for comparing two independent alpha coefficients

Since Cronbach proposed the α coefficient in 1951, researchers have contributed to the derivation of its sampling distribution and the testing of related statistical hypotheses. Yet, there has been no research on effect size index relevant to coefficient α to our knowledge. Considering the importance of effect size in understanding quantitative research findings, we therefore developed an effect size index Δ for the comparison of two independent αs with equal test length based on the asymptotic distribution of under the assumptions of normality and compound symmetry. Simulations indicated that the index was applicable when the sample size was at least 100. The robustness of the derived index when the required assumptions were violated was also explored. It is suggested that the index should be applicable in most cases of unequal test lengths and could be extended to non‐normally distributed component scores. Moreover, a small simulation was conducted to explore the behaviour of Δ with correlated errors, a frequently studied situation violating the assumption of compound symmetry. The proposed index was found to be robust unless a large number of highly correlated errors were present in the data.     

The word concreteness effect occurs for positive,but not negative,emotion words in immediate serial recall

The present study examined the roles of word concreteness and word valence in the immediate serial recall task. Emotion words (e.g. happy) were used to investigate these effects. Participants completed study‐test trials with seven‐item study lists consisting of positive or negative words with either high or low concreteness (Experiments 1 and 2) and neutral (i.e. non‐emotion) words with either high or low concreteness (Experiment 2). For neutral words, the typical word concreteness effect (concrete words are better recalled than abstract words) was replicated. For emotion words, the effect occurred for positive words, but not for negative words. While the word concreteness effect was stronger for neutral words than for negative words, it was not different for the neutral words and the positive words. We conclude that both word valence and word concreteness simultaneously contribute to the item and order retention of emotion words and discuss how Hulme et al.'s (1997) item redintegration account can be modified to explain these findings.     

Decomposing self‐estimates of intelligence: Structure and sex differences across 12 nations

This study examines the structure of self‐estimates of intelligence (SEI) across 12 nations (Australia, Austria, Brazil, France, Iran, Israel, Malaysia, South Africa, Spain, Turkey, UK and US). Participants rated themselves on general and specific abilities from three popular models of intelligence: Gardner's multiple intelligences, Sternberg's triarchic theory of intelligence, and Goleman's emotional intelligence. The results showed that (a) laypeople across nations have similar and invariant concepts of intelligence, (b) concepts of intelligence are cross‐culturally closely related to academic notions of intellectual ability and (c) sex differences in general and specific SEI favouring men are consistent across countries. Male hubris and female humility in SEI seem independent of sex differences in actual cognitive ability and national levels of masculinity‐femininity. Furthermore, international mean differences in general SEI could not be attributed to discrepancies in national intelligence quotient (IQ) levels or to cultural variations.     

Improving self‐regulated learning of preschool children: Evaluation of training for kindergarten teachers

Background In the context of lifelong learning, self‐regulated learning is an important competence. Children between 4 and 6 years of age are at a crucial step in their life to develop self‐regulatory competence. That is why their kindergarten teachers play an important role as instructors as well as role models. Aim This study tested the effects of self‐regulation training for kindergarten teachers concerning their own self‐regulation and methods to foster self‐regulation in children at preschool age whom they were teaching. Sample In this study, 35 German kindergarten teachers and 97 children participated. All adult participants were graduated kindergarten teachers. Method The kindergarten teachers were tested with a questionnaire 2 weeks before and after the training. At the same time, the preschoolers were interviewed. A waiting control group design was applied. Results and conclusions The results obtained by means of analyses of variance show that the self‐regulation of the kindergarten teachers as well as the self‐regulated learning of preschoolers whose kindergarten teachers took part in the training improved significantly. The results indicate that it is possible to improve self‐regulated learning of preschool children by a training programme for kindergarten teachers.     

Iterating between lessons on concepts and procedures can improve mathematics knowledge

Background Knowledge of concepts and procedures seems to develop in an iterative fashion, with increases in one type of knowledge leading to increases in the other type of knowledge. This suggests that iterating between lessons on concepts and procedures may improve learning. Aims The purpose of the current study was to evaluate the instructional benefits of an iterative lesson sequence compared to a concepts‐before‐procedures sequence for students learning decimal place‐value concepts and arithmetic procedures. Samples In two classroom experiments, sixth‐grade students from two schools participated (N = 77 and 26). Method Students completed six decimal lessons on an intelligent‐tutoring systems. In the iterative condition, lessons cycled between concept and procedure lessons. In the concepts‐first condition, all concept lessons were presented before introducing the procedure lessons. Results In both experiments, students in the iterative condition gained more knowledge of arithmetic procedures, including ability to transfer the procedures to problems with novel features. Knowledge of concepts was fairly comparable across conditions. Finally, pre‐test knowledge of one type predicted gains in knowledge of the other type across experiments. Conclusions An iterative sequencing of lessons seems to facilitate learning and transfer, particularly of mathematical procedures. The findings support an iterative perspective for the development of knowledge of concepts and procedures.     

Overweight and cognition

There is a growing concern among health authorities that an increasing number of people in the Western world become overweight and even obese. It is well known that obesity is related to several diseases (e.g., diabetes, stroke, and high blood pressure) and that such diseases related to obesity lead to early death. It has also been discussed whether overweight and obesity in themselves or in relation to such diseases lead to cognitive decline. On the basis of data from a large, population‐based, prospective study we examined three cognitive domains: episodic memory, semantic memory, and spatial ability. Two body measures were used to define normal weight and overweight, body‐mass index and waist/hip ratio. Although these two body measures reveal quite different prevalence data of overweight, the associations between overweight and cognition are similar. For episodic memory, overweight interacts with age, but when controlling for hypertension, stroke and diabetes, this interaction disappears. For semantic memory, normal weight participants outperform overweight participants even after controlling for these diseases. For spatial ability, the well‐established advantage for men holds for young‐old and old‐old normal‐weight participants. For overweight participants, this advantage holds for middle‐age participants only. We conclude that there is a weight‐cognition relationship even after controlling for obesity‐related diseases. The results are discussed in terms of possible biological mechanisms.     

Individual attitudes and perceived social norms: Reports on HIV/AIDS‐related stigma among service providers in China

This study examined HIV/AIDS‐related stigma among Chinese service providers by comparing their personal attitudes toward people living with HIV/AIDS with their perception of social norms related to people living with HIV/AIDS. We randomly selected three provincial hospitals, four city/prefecture hospitals, 10 county hospitals, 18 township health clinics, and 54 village clinics from Yunnan, China. Doctors and nurses were randomly sampled proportionally to the doctor–nurse ratio of each hospital or clinic. Lab technicians were over‐sampled in order to include an adequate representation in the analysis. A total of 1,101 service providers participated in a voluntary, anonymous survey where demographic characteristics, individual attitude and perceived social norms toward people living with HIV/AIDS, discrimination intent at work, general prejudicial attitude and knowledge on HIV/AIDS were measured. A majority of the sample demonstrated a similarity between their personal views and what they thought most people in society believe. Multiple logistic regressions revealed that participants who were younger or reported personal contact with people living with HIV/AIDS were significantly more likely to report personal attitudes toward the population that were more liberal than their perceived social norms. Holding a more liberal personal attitude toward people living with HIV/AIDS than perceived social norms was significantly and negatively related to the level of discrimination intent at work, perceived discrimination at interpersonal level and the level of general prejudicial attitude toward people living with HIV/AIDS. Results underscored the importance of understanding social norms and personal attitudes in studying HIV‐related stigma and called for the incorporation of existing human capital into future HIV stigma reduction programs.