Fixed and variable ratios and delays: Further tests of an equivalence rule.

A discrete-trial procedure was used to measure 4 White Carneaux pigeons' choices between FR and VR schedules and between fixed and variable delays before reinforcement. A peck at a green key produced a reinforcement schedule that was constant within a condition but varied across conditions. A peck at a red key produced a ratio schedule (or, in other conditions, a simple delay) whose size was increased or decreased many times a session, depending on the S's previous choices. The purpose of these adjustments was to estimate an indifference point—a ratio size (or delay duration) at which the S chose each key about equally often. The results were used to test the present author's (see record 1985-19333-001) equivalence rule for choices between fixed and variable schedules. This rule predicted the major trends in the obtained indifference points from both ratio and delay conditions, but better predictions were generated with a more complex equation that included parameters reflecting the Ss' sensitivities to delay of reinforcement and to events of different probabilities. It is concluded that a successful equivalence rule must include parameters that can be adjusted to describe the effects of delay and probability in a given experimental setting. Once these parameters are estimated, however, choices involving both fixed and variable delays and FRs and VRs can be accurately predicted with the same equation. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Validity" of short-form intelligence tests.

A short-form intelligence test is commonly "validated" by demonstrating a high correlation between it and the full scale from which it is taken. It has been argued, however, that the correlation between the short form and the full scale is less meaningful than the extent to which they agree in classifying individuals as to intellectual level; the latter depends in part upon the width of the categories in the classification system. A table is provided which shows the theoretical agreement between the short form and the full scale as a function of their correlation and category width. Empirical values from two studies approximate fairly closely the values given in this table. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Predictive Validity of Self-Efficacy in Training Performance: Little More Than Past Performance.

Past research on the influence of self-efficacy in training has provided mixed results. Key differences between studies pertain to whether past performance is operationalized as a residual variable or as an unadjusted variable and to the type of task used. In this study, the authors conducted and performed a reanalysis to examine the influence of self-efficacy using both operationalizations of past performance in 2 experimental tasks. Results indicate that, regardless of task version or type, self-efficacy predicted performance only when a residual measure of past performance was used, but not when past performance was unadjusted. However, when past performance was adjusted, the findings for self-efficacy were likely a statistical artifact. These results suggest that self-efficacy is a consequence rather than a cause of performance in training. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Power and sample size calculations for studies involving linear regression

This article presents methods for sample size and power calculations for studies involving linear regression. These approaches are applicable to clinical trials designed to detect a regression slope of a given magnitude or to studies that test whether the slopes or intercepts of two independent regression lines differ by a given amount. The investigator may either specify the values of the independent (x) variable(s) of the regression line(s) or determine them observationally when the study is performed. In the latter case, the investigator must estimate the standard deviation(s) of the independent variable(s). This study gives examples using this method for both experimental and observational study designs. Cohen's method of power calculations for multiple linear regression models is also discussed and contrasted with the methods of this study. We have posted a computer program to perform these and other sample size calculations on the Internet (see http://www.mc.vanderbilt.edu/prevmed/psintro+ ++.htm). This program can determine the sample size needed to detect a specified alternative hypothesis with the required power, the power with which a specific alternative hypothesis can be detected with a given sample size, or the specific alternative hypotheses that can be detected with a given power and sample size. Context-specific help messages available on request make the use of this software largely self-explanatory.     

Concrete Fracture Process Zone Characterization with Fiber Optics

The characterization of the fracture process zone inside a cracked concrete specimen is investigated through optical fiber technology. Fiber Bragg gratings are used to measure the strains in the close vicinity of the crack front, thus enabling us (for the first time) to directly measure those deformations inside the concrete specimen. A detailed discussion of the experimental technique is first provided. Then, following the experimental measurements, test results are presented and discussed. Preliminary results indicate that there is a narrow zone on each side of the crack front with inelastic residual strains, and another where strains increase only in the presence of a neighboring crack tip. The width of the process zone is found to be about three times the maximum aggregate size.     

Statistical Guidelines for Curve Number Generation

The accuracy of runoff curve numbers (CNs) is unknown, and empirical evidence has suggested that with the current CN table, hydrological systems are being over designed—which some believe is due to a variable known as the initial abstraction coefficient (λ). Therefore, guidelines to produce a new CN table are needed. In order to develop this set of guidelines, the following objectives were met: Determination of CN and λ sensitivity, assessment of the accuracy of alternative methods for determining CNs, examination of the effect of the range of data, and evaluation of the potential change in hydrologic design due to a new table. Using measured and simulated data, the methods of estimating the CN were evaluated and assessed for accuracy. A new method using concepts of lognormal frequency was developed and found to be more accurate than the current practices. It was also found that λ is an insensitive variable when compared to the CN, and therefore, may complicate the optimal fitting of the CNs. Finally, it was determined that developing a new CN table would affect the estimation of peak discharge rates, and thus hydrologic designs. Therefore, it may be advantageous to develop a new CN table based on peak discharge measurements rather than depths of rainfall and runoff. Guidelines that should lead to a revised CN model with improved accuracy are provided.     

Multiple correlation: Exact power and sample size calculations.

This article discusses power and sample size calculations for observational studies in which the values of the independent variables cannot be fixed in advance but are themselves outcomes of the study. It reviews the mathematical framework applicable when a multivariate normal distribution can be assumed and describes a method for calculating exact power and sample sizes using a series expansion for the distribution of the multiple correlation coefficient. A table of exact sample sizes for level .05 tests is provided. Approximations to the exact power are discussed, most notably those of J. Cohen (1977). A rigorous justification of Cohen's approximations is given. Comparisons with exact answers show that the approximations are quite accurate in many situations of practical interest. More extensive tables and a computer program for exact calculations can be obtained from the authors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Analysis-of-Variance Tests in the Analysis and Comparison of Curves.

The purpose of this paper is to extend methods presently available for use in the analysis and the comparison of curves obtained in psychological experiments. The reader will be assumed to have a general acquaintanceship with analysis-of variance techniques at an elementary level, such as could be obtained from most of the better available textbooks. The present paper will deal with the analysis of curves that result when the difference between experimental treatments involves a scaled independent variable with equal steps (or equal-logarithmic steps) between levels of the independent variable. Examples would be learning curves, extinction curves, dark adaptation curves, time-to-attain a level of dark adaptation as a function of the luminance of the preadaptation field, response rate as a function of the amount of reinforcement, etc. The procedures apply to most curves or sets of curves in which y, the dependent variable, is plotted as a function of x, the independent variable, where there are equal intervals between the values of x. It is assumed that there is random normal variation in the dependent variable at each data point with equal error variances. There may or may not be parameters expressing qualitative or quantitative variation of additional independent variables that are orthogonal to x. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The adaptation and use of Kendall's Coefficient of Concordance (W) to sociometric-type rankings.

Kendall's W, an index of agreement among n rankings, requires that all members be ranked. In this paper, W is modified to omit self-ranks, allowing for easier interpretation of W. A table is provided, indicating the values of W needed to achieve significance at the 5% and 1% levels, for values of n (number of objects ranked) from 4 through 15, hence enabling one to test the hypothesis of independence among rankings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Simultaneous Prediction of Saturated Hydraulic Conductivity and Drainable Porosity Using the Inverse Problem Technique

The saturated hydraulic conductivity K and the effective porosity f are two important input parameters needed for lateral drain spacing design, as well as some other applications. The technical and economic justification, of most drainage projects, is mainly connected to these two parameters. The current design procedure is based upon calculation of the lateral spacing, using some average values of K and f within the drainage area. The objectives of this study were to introduce a new method for simultaneous estimation of K and f parameters using the inverse problem technique, and to evaluate five different unsteady drainage analytical models of the Boussinesq equation, suggested by different researchers for simultaneous prediction of the parameters. Consequently, five different analytical models for predicting water table profiles were solved, using the inverse problem technique. Each model was then evaluated. A physical drainage model of 2.2?m length, 0.3?m width, and 0.5?m height was established in the laboratory and carefully packed with a sandy loam soil. A perforated drainage pipe of 4.5?cm in diameter was installed at the bottom end of the model. Many piezometers were inserted in the soil for spatial and temporal water table monitoring. Different data sets from the experiments and literature were used for model calibration. The newly proposed approach that is based upon measuring water table profiles, at different times, was then evaluated with both constant and variable f. The predicted values of the proposed approach indicated reasonable agreement with the measured data. With variable effective porosity, the method was even more accurate to predict the water table profiles. Using the inverse problem technique, all the analytical models provided good agreement with the measured data. Among these, however, the Topp and Moody model predicted more accurate results than other models.     

Size constancy of adolescent schizophrenics.

In a size-constancy task 10 schizophrenic and 10 normal adolescent males judged variable triangles as smaller, same size, or larger than a standard. The schizophrenics' judgments were further from constancy, and differed qualitatively. They made more (a) same-size judgments, (b) changes of judgments, (c) overestimation of the size of the standard, and (d) improvement with practice. The relative constancy of the same-size judgments of most Ss suggested the effects of personality variables. A significant correlation was found between constancy performance and the Sc score on the MMPI for the experimental group. The direction of error, underconstancy or overconstancy, was determined by the space arrangement of the variable and the standard. Both groups responded similarly to the experimental conditions of distance, series order, and space arrangement. (22 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Parametric statistics and levels of measurement: Factorial designs and multiple regression.

Let Y be a continuous, ordinal measure of a latent variable Θ. In general, for factorial designs, an analysis of variance of the observed variable Y cannot be used to draw inferences about main effects and interactions on the latent variable Θ even when the standard normality and equality of variance assumptions hold. If Y is a continuous, ordinal measure of a latent variable Θ; X?,…, Xn are continuous, ordinal measures of latent variables Φ?,…, Φn; and the observed measures have a multivariate normal distribution, then a multiple regression analysis of the observed criterion measure Y and predictors X?,…, Xn can be used to test hypotheses about multivariate associations among the latent variables. Furthermore, the predicted values Y′ are unbiased estimates of quantities that are monotonically related to predicted values on the latent criterion variable Θ. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ductal carcinoma in situ: introduction of the concept of ductal intraepithelial neoplasia

The current definition, diagnostic criteria, grading, and approach to assessment of extent of ductal carcinoma in situ (DCIS) are presented. The problem areas, particularly the difficulties in separating low-grade DCIS from atypical intraductal hyperplasia (AIDH), accurate assessment of size and/or extent of DCIS, and their impact on patient management are critically reviewed. On the basis of the route of progression of DCIS, recently confirmed by three-dimensional reconstructed models, an optimal and simple approach to uniform excision, orientation, and processing of biopsy samples is presented. Emphasis is placed on the role of intraductal proliferative lesions (IDH, AIDH, and DCIS) as risk factors of variable magnitude in subsequent development of invasive breast carcinoma. It is proposed that these proliferations should be classified as "mammary intraepithelial neoplasia, ductal type" or as "ductal intraepithelial neoplasia" (DIN); the rational for the application of this classification system is provided. This approach obviates the current separation of AIDH and low-grade DCIS into two very drastically different categories of cancer and non-cancer without interfering with appropriate management of the various lesions. The DIN classification is presented in a simple translational table, along with the current terminology for various lesions.     

Combining 2 x 2 tables that contain structural zeros

When one cell or more of a contingency table is necessarily zero, the table is said to contain structural zeros. These structural voids may be inherent to the problem at hand, or, in some applications, they may be introduced intentionally through the experimental design. With data classified by a third stratification variable, one needs a method for analysing a set of independent 2 x 2 tables. We propose Cochran-Mantel-Haenszel type analyses that combine observations across strata. We also propose tests of hypotheses pertaining to the marginal and conditional probabilities.     

When small effects are impressive.

Effect size is becoming an increasingly popular measure of the importance of an effect, both in individual studies and in meta-analyses. However, a large effect size is not the only way to demonstrate that an effect is important. This article describes 2 alternative methodological strategies, in which importance is a function of how minimal a manipulation of the independent variable or how difficult-to-influence a dependent variable will still produce an effect. These methodologies demonstrate the importance of an independent variable or psychological process, even though they often yield effects that are small in statistical terms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Design and analysis of experiments contrasting the within- and between-subjects manipulation of the independent variable.

The assumption is often made that one may perform an experiment by manipulating the independent variable within Ss or between Ss and that the effect of the independent variable would be the same in the 2 types of experiments. Many experiments in different areas of psychology show that this assumption is often false. In these experiments the design type is treated as an explicit independent variable in a factorially designed experiment. The outcome of these experiments is that there is an interaction between the design type and the substantive independent variable. These experiments are generally inefficiently designed or the results are poorly analyzed. The present paper develops a proper analysis of variance procedure for the analysis of the results of such an experiment and indicates a more efficient experimental design. A computational example is given. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Foundation Isolation for Seismic Protection Using a Smooth Synthetic Liner

Smooth synthetic materials placed underneath foundations of structures can provide seismic protection by absorbing energy through sliding. Cyclic and shaking table tests were conducted on a variety of synthetic interfaces to identify a suitable liner for use as foundation isolation. It was concluded that a high strength, nonwoven geotextile placed over an ultrahigh molecular weight polyethylene, UHMWPE (geotextile/UHMWPE) constitutes a liner that is well suited for this application. The static friction coefficient of the interface (between the geotextile and the UHMWPE) is about 0.1. The dynamic coefficient is about 0.07 and is insensitive to changes in slip rate and normal stress. A single-story structural model with and without foundation isolation was tested using a shaker table. The results demonstrate the role of foundation isolation in substantially reducing the seismic shear forces in the model. Accompanying this reduction in shear forces are slip displacements along the isolation liner. Permanent slip (final location of the structure relative to its initial position) can be reduced through the use of a small restoring force that could be provided through passive soil resistance. Peak-to-peak slip (maximum slip during shaking) needs to be permitted for foundation isolation to be effective. The experimental and analytical research results demonstrate the technical feasibility of using a smooth synthetic liner in earthquake hazard mitigation.     

Morphology relations during surface-transport controlled sintering

Precise geometrical relationships have been calculated for the surface-transport controlled sintering of sphere to sphere configurations. A minimum surface area neck configuration is assumed and interparticle coordination is considered. The calculated results for surface-transport controlled sintering show a small particle size reduction during neck growth. In contrast, the concurrent surface area reduction is shown to be significantly large. Based on the morphology results of these calculations, an empirical expression relating neck size and coordination to surface area has been derived. Thus, surface area is proposed to be an alternative measure to neck size during surface-transport controlled sintering studies. Previous experimental results are generally in good agreement with the calculations provided by the proposed model.     

Continuous symmetry: a model for human figural perception

Symmetry is usually viewed as a discrete feature: an object is either symmetric or non-symmetric. In this presentation, symmetry is treated as a continuous feature and a continuous measure of symmetry (the Symmetry Distance) is defined. This measure can be easily evaluated for any shape or pattern in any dimension. A preliminary study presented here shows that the Symmetry Distance is commensurate with human perceptual experience. Good correlation is found between the continuous symmetry values and the perceived goodness of figures.     

L'imipramine dans le traitement par exposition de l'agoraphobie: Un examen critique de la littérature.

Reviews several studies on the use of imipramine and exposure-based methods for the treatment of agoraphobia. The overall results of this literature review indicate that combined imipramine–exposure treatment is superior to imipramine pharmacotherapy alone. A table listing authors, Ss, experimental conditions, measurement techniques, and results of 10 studies on agoraphobia is provided. (English abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)