Statistical power in complex experimental designs

We show that power and sample size tables developed by Cohen (1988, pp. 289–354, 381–389) produce incorrect estimates for factorial designs: power is underestimated, and sample size is overestimated. The source of this bias is shrinkage in the implied value of the noncentrality parameter, λ, caused by using Cohen’s adjustment ton for factorial designs (pp. 365 and 396). The adjustment was intended to compensate for differences in the actual versus presumed (by the tables) error degrees of freedom; however, more accurate estimates are obtained if the tables are used without adjustment. The problems with Cohen’s procedure were discovered while testing subroutines in DATASIM 1.2 for computing power and sample size in completely randomized, randomized-blocks, and split-plot factorial designs. The subroutines give the user the ability to generate power and sample size tables that are as easy to use as Cohen’s, but that eliminate the conservative bias of his tables. We also implemented several improvements relative to “manual” use of Cohen’s tables: (1) Since the user can control the specific values of 1- β,n, andf used on the rows and columns of the table, interpolation is never required; (2) exact as opposed to approximate solutions for the noncentralF distribution are employed; (3) solutions for factorial designs, including those with repeated measures factors, take into account the actual error degrees of freedom for the effect being tested; and (4) provision is made for the computation of power for applications involving the doubly noncentralF distribution.     

Metacognition reconsidered: Implications for intervention research

Metacognitive training techniques have been used successfully to improve children's problem-solving skills. The concept of metacognition needs further refinement, however, if it is to continue to be useful as an explanatory construct. Specifically, we argue that more attention needs to be paid to how metacognitive abilities are acquired, how this knowledge could be used to help improve the performance of children with learning difficulties, and how metacognition may be related to other self-evaluation processes.This paper was completed with support from the National Institute of Child Health and Human Development (Grant HD05951), and from the Department of Education (Grant 00840068). We would like to express our appreciation and thanks to Joseph Campione and to Annemarie Palinscar, who patiently listened to, and frequently commented upon, the ideas presented in this paper.     

Functional Impulsivity and Speeded Ability Test Performance

The current study examines the influence of functional impulsivity on speeded ability test performance. As predicted, functional impulsivity was positively related to number of items attempted (i.e., speed), but its impact on total score was more complex. In particular, analysis of the relations between ability, functional impulsivity and accuracy revealed evidence of a suppressor effect. Specifically, functional impulsivity was found to be negatively related to accuracy, but only after ability differences were controlled. Taken as whole, the current results suggest functional impulsivity may influence test‐taking behavior, but it likely does not result in a systematic influence on observed scores. Directions for further research needed to clarify these relations are discussed.     

Comparing Group-Contingency and Individualized Equivalence-Based Instruction to a PowerPoint Lecture to Establish Equivalence Classes of Reinforcement and Punishment Procedures with College Students

The Psychological Record - Equivalence-based instruction (EBI) involves the teaching of socially relevant material (e.g., academic material) with stimulus equivalence procedures. In the research...     

Training Staff to Create Equivalence-Based Instruction Materials in Qualtrics

The Psychological Record - Staff training is an important line of research to ensure that clinicians in the field of applied behavior analysis provide quality services. One approach to providing...     

Lower limb kinematic variability in dancers performing drop landings onto floor surfaces with varied mechanical properties

Elite dancers perform highly skilled and consistent movements. These movements require effective regulation of the intrinsic and extrinsic forces acting within and on the body. Customized, compliant floors typically used in dance are assumed to enhance dance performance and reduce injury risk by dampening ground reaction forces during tasks such as landings. As floor compliance can affect the extrinsic forces applied to the body, secondary effects of floor properties may be observed in the movement consistency or kinematic variability exhibited during dance performance. The aim of this study was to investigate the effects of floor mechanical properties on lower extremity kinematic variability in dancers performing landing tasks. A vector coding technique was used to analyze sagittal plane knee and ankle joint kinematic variability, in a cohort of 12 pre-professional dancers, through discrete phases of drop landings from a height of 0.2 m. No effect on kinematic variability was observed between floors, indicating that dancers could accommodate the changing extrinsic floor conditions. Future research may consider repeat analysis under more dynamic task constraints with a less experienced cohort. However, knee/ankle joint kinematic variability was observed to increase late in the landing phase which was predominantly comprised of knee flexion coupled with the terminal range of ankle dorsiflexion. These findings may be the result of greater neural input late in the landing phase as opposed to the suggested passive mechanical interaction of the foot and ankle complex at initial contact with a floor. Analysis of joint coordination in discrete movement phases may be of benefit in identifying intrinsic sources of variability in dynamic tasks that involve multiple movement phases.     

An Empirical Note on the Role of Verbal Labels in Motor Short-Term Memory Tasks

Previous studies of motor short-term memory have shown that when a criterion movement on a semicircular positioning task is accompanied by an appropriate verbal label (a clock-face position), recall of the movement is more accurate than when only the movement is presented. This increased accuracy could be due to either the additional spatial information provided by the label or enhanced retention of the movement information. These two alternatives cannot be distinguished on the basis of previous studies because the studies have not evaluated movement accuracy following presentation of the label alone. The present study employed such a condition in addition to the movement-only and movement-plus-label conditions to distinguish between the two hypotheses. In all conditions, subjects were asked to move to the criterion position after a retention interval of either 5 sec or 60 sec. Evidence indicated that subjects who received both the label and the movement tended to use the spatial information provided by the label at the 60-sec interval. The evidence did not indicate that the verbal label actually enhanced retention of the movement information.     

A Closer Look at Reactions to Realistic Recruitment Messages

Recently there has been a great deal of interest among consumer and behavioral judgment researchers on how immediate affective reactions influence overall evaluations. The current study seeks to determine whether immediate affective reactions to organizational attributes warrant the attention of recruitment researchers as well. Using a customized web‐based computer program that elicits immediate affective reactions to organizational previews, the study finds that overall evaluations of the organization are influenced more by the average intensity of immediate affective reactions experienced during the message than by the relative balance of positive and negative information contained in the message. Results suggest that practitioners using realistic information need to be more concerned about the average intensity of recipients' reactions than about the relative balance of positive or negative information.