There has been growing interest in using statistical methods to analyze data and estimate effect size indices from studies that use single-case designs (SCDs), as a complement to traditional visual inspection methods. The validity of a statistical method rests on whether its assumptions are plausible representations of the process by which the…

It is more common for educational and psychological data to be nonnormal than to be approximately normal. This tendency may lead to bias and error in point estimates of the Pearson correlation coefficient. In a series of Monte Carlo simulations, the Pearson correlation was examined under conditions of normal and nonnormal data, and it was compared…

This article describes psychometric testing of an Icelandic adaptation of the "Adult Reading History Questionnaire" (ARHQ), designed to detect a history of reading difficulties indicative of dyslexia. Tested in a large and diverse sample of 2,187 adults, the Icelandic adaptation demonstrated internal consistency reliability (Cronbach's…

In light of the emergence of statistical analysis techniques based on data mining in education sciences, and the potential they offer to detect non-trivial information in large databases, this paper presents a procedure used to detect factors linked to academic achievement in large-scale assessments. The study is based on a non-experimental,…

We propose a new limited-information goodness of fit test statistic C[subscript 2] for ordinal IRT models. The construction of the new statistic lies formally between the M[subscript 2] statistic of Maydeu-Olivares and Joe (2006), which utilizes first and second order marginal probabilities, and the M*[subscript 2] statistic of Cai and Hansen…

The sizable gender gap in college enrolment, especially among African Americans, constitutes a puzzling empirical regularity that may have serious consequences on marriage markets, male labor force participation and the diversity of college campuses. For instance, only 35.7 percent of all African American undergraduate students were men in 2004.…

The Census Bureau has historically grouped high school diploma holders along with those who hold "high school equivalent" credentials. Among these is the credential earned through successfully passing the General Education Development (GED) test. Interest in identifying those with GEDs has recently increased, in part from debate within…

Concentrations of chemical substances and microorganisms are often averaged using geometric means. Argues that the arithmetic mean is a better choice for summarizing data because arithmetic means are unbiased, easier to calculate and understand, scientifically more meaningful, and more protective of public health. Results of a simulation study…

The problem of monitoring trends for changes at unknown times is considered. Statistics that permit one to focus high power on a segment of the monitored period are studied. Numerical procedures are developed to compute the null distribution of these statistics. (Author)

Effectiveness ratings of principals by researchers have frequently been hampered by relying on teachers' one-dimensional, research-triggered "global" ratings. This paper reports a 1979-80 British Comumbia superintendents' study geared toward multidimensional subjective assessments of 266 administrators, and concentrates primarily on ways…

Several techniques have been developed for creating continuous smooth distributions of test norms. This paper describes two studies that explore the behavior of cubic splines in order to determine their appropriateness for use in test norming. The first study uses data from the Curriculum Referenced Tests of Mastery (CRTM) and employs two…

This manual is a first effort to begin to identify, describe, and develop procedures for assessing various aspects of digital reference service. Its overall purpose is to improve the quality of digital reference services and assist librarians to design and implement better digital reference services. More specifically, its aim is to: assist…