Properties of the Spearman correction for attenuation were investigated using Monte Carlo methods, under conditions where correlations between error scores exist as a population parameter and also where correlated errors arise by chance in random sampling. Equations allowing for all possible dependence among true and error scores on two tests at…

The growth curve model has been a useful tool for the analysis of repeated measures data. However, it is designed for an aggregate-sample analysis based on the assumption that the entire sample of respondents are from a single homogenous population. Thus, this method may not be suitable when heterogeneous subgroups exist in the population with…

Background: Based on standard social benefit registers, the prevalence of intellectual disability (ID) in Finland is estimated to be 0.6%, while epidemiological surveys yield 1.1%. Combining several registers, our aim was to find a more reliable estimate of the prevalence of ID, especially among children and adolescents. This is important when…

This paper, the second of a two part article, expands on an idea that appeared in literature in the 1950s to show that by restricting the domain to those complex numbers that map onto real numbers, representations of functions other than the ones in the real plane are obtained. In other words, the well-known curves in the real plane only depict…

Various efforts are being made to introduce the different physical aspects and uses of computational chemistry to the undergraduate chemistry students. A new laboratory approach that demonstrates all such aspects via experiments has been devised for the purpose.

Based on the recent three population censuses of China, in this article, we used life table technique to compute the expected years of working life for the Chinese labor force in the primary, secondary and tertiary industries in 1982, 1990 and 2000. We found, after two decades of economic reform, the expected years of working life in the primary…

The theory of signal detection is convenient for measuring mnemonic ability in recognition memory paradigms. In these paradigms, randomly selected participants are asked to study randomly selected items. In practice, researchers aggregate data across items or participants or both. The signal detection model is nonlinear; consequently, analysis…

A number of methods are available in the literature to measure confidence intervals. Here, confidence intervals for estimating the population mean of a skewed distribution are considered. This note proposes two alternative confidence intervals, namely, Median t and Mad t, which are simple adjustments to the Student's t confidence interval. In…

A method called the Remainder Method is proposed for the calculation of sample quantiles of a given order, for example, quartiles, hexatiles, octatiles, deciles and percentiles assuming that all the observations are distinct. Proof is given for a special case of deciles. The criterion "equisegmentation" is proposed, namely that the number of…

Following the analytical approach suggested in Campbell, the authors consider a baseline real-business-cycle (RBC) model with endogenous labor supply. They observe that the coefficients in the loglinear approximation of the dynamic equations characterizing the equilibrium are related to the fundamental parameters in a relatively simple manner.…

In this study, the authors assess several strategies created on the basis of the Mantel-Haenszel (MH) procedure for conducting differential item functioning (DIF) analysis with small samples. One of the analytical strategies is a loss function (LF) that uses empirical Bayes Mantel-Haenszel estimators, whereas the other strategies use the classical…

This article presents a rich geometry problem and discusses its solution. A variety of mathematically correct justifications for this answer are provided. (Contains 2 figures.)

This study compares the performance of three nonparametric item characteristic curve (ICC) estimation procedures: isotonic regression, smoothed isotonic regression, and kernel smoothing. Smoothed isotonic regression, employed along with an appropriate kernel function, provides better estimates and also satisfies the assumption of strict…

The students of the targeted fourth, fifth, sixth, and ninth grade classes exhibited difficulties with number sense that interfered with understanding and recall of basic math facts. Evidence for the existences of the problem included teacher observation, test scores, and student and teacher surveys. The research participants included 42 children…

Has it ever seemed to you that some students are hardwired to dislike math? If so, then here's a book that explains how negative attitudes toward math get established in the brain and what you can do to turn those attitudes around. Math teacher and neurologist Judy Willis gives you over 50 strategies you can use right away in any grade level to:…