The derivation of a brief Student Nurse Stress Index

The lack of an adequate measure of perceived sources of stress for student nurses led to the construction of the Student Nurse Stress Index (SNSI). Responses from 235 first-year student nurses to 35 items from the Beck and Srivastava Stress Inventory (Beck, and Srivastava, 1991), and 15 new items, were subjected to exploratory factor analysis using principal components analysis and oblimin rotation. A reliable 22-variable solution with a simple oblique structure including Academic load, Clinical sources, Interface worries, and Personal problems factors was obtained in this initial sample, and confirmed at an exploratory level in a further independent validation sample of 188 first-year students. Confirmatory factor analysis established the four-factor model in the first sample, but required that three variables load onto more than one factor. This more complex four-factor model was confirmed using independent data from the validation sample, and the total invariance of factor loadings and factor covariances of this more complex four-factor model was established in both data sets simultaneously using multi-sample techniques. The SNSI shows cross-sample factor congruence, good internal reliabilities, and concurrent and discriminant validity across a range of reporting conditions.     

Don't mention Stonehenge!

It rises massive and magnificent above Salisbury Plain. The extraordinary monoliths of Stonehenge leave us as impressed today as ever—and as baffled. Archaeologists argue about how it was made. Can statisticians tell the answer? Chris Jones thinks they can be of considerable assistance.     

Adjusted estimates for time-to-event endpoints

In the analysis of retrospective data or when interpreting results from a single-arm phase II clinical trial relative to historical data, it is often of interest to show plots summarizing time-to-event outcomes comparing treatment groups. If the groups being compared are imbalanced with respect to factors known to influence outcome, these plots can be misleading and seemingly incompatible with results obtained from a regression model that accounts for these imbalances. We consider ways in which covariate information can be used to obtain adjusted curves for time-to-event outcomes. We first review a common model-based method and then suggest another model-based approach that is not as reliant on model assumptions. Finally, an approach that is partially model free is suggested. Each method is applied to an example from hematopoietic cell transplantation.     

D-efficient window experimental designs

In the paper we present a new method of calculating sampling intervals, so-called windows, allowing an experimenter some flexibility in timing the sample collection, while a minimum required design efficiency for parameter estimation is assured. The method is based on the Equivalence Theorem for D-optimality what makes the length of each window related to the parameter sensitivities. An example of calculating the windows in a pharmacokinetic study is presented. Some other methods of calculating efficient sampling windows are briefly discussed.     

Estimating conditional tail expectation with actuarial applications in view

We develop statistical inferential tools for estimating and comparing conditional tail expectation (CTE) functions, which are of considerable interest in actuarial science. In particular, we construct estimators for the CTE functions, develop the necessary asymptotic theory for the estimators, and then use the theory for constructing confidence intervals and bands for the functions. Both parametric and non-parametric approaches are explored. Simulation studies illustrate the performance of estimators in various situations. Results are obtained under minimal assumptions, and the general Vervaat process plays a crucial role in achieving these goals.     

Experiencing Work: Values, Attitudes, and Moods

This paper describes a model (the VAM model)which integrates three of the most significantdimensions of the work experience, work values,attitudes, and moods, into one overarching framework.The VAM model proposes that a rich and more completeunderstanding of the experience of work necessitates thesimultaneous consideration of work values, attitudes,and moods. After describing how work values, attitudes, and moods, each capture key aspects ofexperiencing work, we discuss three important dimensionsalong which they vary: time, dynamism, and focus. Thesedimensions underscore the need for the simultaneous consideration of values, attitudes, and moodsfor a fuller understanding of the work experience. Wethen describe how work values, attitudes, and moods havethe potential to influence each other. Finally, we discuss the implications of the VAM modelfor understanding important organizational outcomesincluding extra-role behavior, job performance, socialloafing, absenteeism, and turnover.     

The Protestant Ethic: Weber s Model and the Empirical Literature

Empirical research with regard to the Protestantethic is reviewed in relation to Weber s model of thepart a specifically religious ethos played in the riseof capitalism. Weber argued that Western legal and commercial changes were not in themselvesan adequate explanation. Essential also was the set ofvalues emphasized by ascetic Protestantism:self-discipline, hard work, the careful use of time, the reinvestment of one s gains, personal honesty,creative innovation, and faith in the rewards of a justGod. Empirical research has found positive correlationsbetween Protestant ethic values and internal locus of control (self-discipline), hard work,honesty, and belief in a just world. Findings withregard to the use of time and money are inconclusive.The relationship with creative innovation has not been examined. There is a need for empiricalstudy of the relationship between the Protestant ethicand personal religious orientation.     

Low-Income Mothers' Conversations About Emotions and Their Children's Emotional Competence

This study examined the linkage between low-income mothers' conversations about emotions and their children's understanding of emotion. Forty-five low-income preschoolers and their mothers were videotaped while viewing a wordless picture book designed to elicit talk about emotions. Three maternal and child emotional language behaviors were coded from the videotapes: (a) unelaborated comments about emotions; (b) explanations about the causes and consequences of emotions; and (c) empathy-related statements. The children's questions about emotions were also coded. In a separate interview, the preschoolers were administered tasks that assessed emotional expression knowledge, emotional situation knowledge, and emotional role-taking. The results revealed that emotional situation knowledge was positively predicted by mothers' empathy-related statements. Mothers' explanations about the causes and consequences of emotions were uniquely related to emotional role-taking ability. There were very few correlations between the mothers' and children's talk about emotions. Results are discussed in terms of the functional significance of mothers' emotional language for young children's emotional competence.     

Estimating time to detect time trends in continuous cropping

SUMMARY In long-term field trials comparing different sequences of crops and husbandry practices, the identification and understanding of trends in productivity over time is an important issue of sustainable crop production. This paper presents a statistical technique for the estimation of time trends in yield variables of a seasonal annual crop under continuous cropping. The estimation procedure incorporates the correlation structure, which is assumed to follow first-order autocorrelation in the errors that arise over time on the same plot. Because large differences in annual rainfall have a major effect on crop performance, rainfall has been allowed for in the estimation of the time trends. Expressions for the number of years (time) required to detect statistically significant time trends have been obtained. Illustrations are based on a 7-year data set of grain and straw yields from a trial in northern Syria. Although agronomic interpretation is not intended in this paper, the barley yield data indicated that a significant time trend can apparently be detected even in a suboptimal data set of 7 years' duration.