To date, small sample problems with latent growth models (LGMs) have not received the amount of attention in the literature as related mixed-effect models (MEMs). Although many models can be interchangeably framed as a LGM or a MEM, LGMs uniquely provide criteria to assess global data-model fit. However, previous studies have demonstrated poor…

The purpose of this paper is to develop a more general method for sample recruitment in experiments that is purposive (not random) and that results in a sample that is compositionally similar to the generalization population. This work builds on Tipton et al. (2011) by offering solutions to a larger class of problems than the non-overlapping…

A jack knife is a pocket knife that is put to many tasks, because it's ready to hand. Often there could be a better tool for the job, such as a screwdriver, a scraper, or a can-opener, but these are not usually pocket items. In statistical terms, the expression implies making do with what's available. Another simile, of an extreme situation, is…

This study serves as a teaching aid for teachers of introductory statistics. The aim of this study was limited to determining various sample sizes when estimating population proportion. Tables on sample sizes were generated using a C[superscript ++] program, which depends on population size, degree of precision or error level, and confidence…

In this article we describe a semester-long project, based on the popular video game series Guitar Hero, designed to introduce upper-level undergraduate statistics students to statistical research. Some of the goals of this project are to help students develop statistical thinking that allows them to approach and answer open-ended research…

This article proposes 2 new approaches to test a nonzero population correlation ([rho]): the hypothesis-imposed univariate sampling bootstrap (HI) and the observed-imposed univariate sampling bootstrap (OI). The authors simulated correlated populations with various combinations of normal and skewed variates. With [alpha[subscript "set"]]=0.05, N…

Adjustment methods such as propensity scores and analysis of covariance are often used for estimating treatment effects in nonexperimental data. Shadish, Clark, and Steiner used a within-study comparison to test how well these adjustments work in practice. They randomly assigned participating students to a randomized or nonrandomized experiment.…

In some linear regression problems samples may be unwittingly drawn from a heterogeneous population. The exploratory procedure described in this paper can be used to detect heterogeneity in a regression problem associated with the intercept. (Author)

Some sampling characteristics of three estimators of the intraclass correlation were investigated under a variety of conditions within the context of a one-way analysis of variance. The results promote caution in the use of all three estimators. The three estimators differed very little in their bias or in their standard errors. (Author/JKS)

Information loss occurs when continuous data are grouped in discrete intervals. After calculating the squared correlation coefficients between continuous data and corresponding grouped data for four population distributions, the effects of population distribution, number of intervals, and interval width on information loss and recovery were…

A small data set is used to show that correlations and standard deviations measured within an explicitly selected group need not be smaller than those within an applicant population. Both validity and reliability estimates within a selected group can exceed those within an applicant population. (Author/LMO)

Addresses issue of range enhancement effects on correlations, asserting that, while adding to or deleting from sample can affect variance and correlation in sample, increases or decreases in individual differences in intact sample resulting from such factors as history, maturation, training, and experience will not necessarily affect correlations.…

This article presents an improved approximation formula for the problem of correcting correlation coefficients that arise from range-restricted distributions on either or both the independent and dependent variable. (BS)

Presents a method for determining the number of days on which questions must be counted in order to achieve a given precision and confidence in reference statistics. (Author/PF)