A test of two refinements in procedures for meta-analysis.

This study used Monte Carlo simulation to examine the increase in accuracy resulting from 2 statistical refinements of the interactive Schmidt-Hunter procedures for meta-analysis: the use of the mean correlation instead of individual correlations in the estimation of sampling error variance, and a procedure that takes into account the nonlinear nature of the range-restriction correction. In all of the cases examined, these refinements increased the accuracy of the interactive procedure in estimating the variance of population correlations and resulted in more accuracy than other procedures examined. The use of the mean correlation in the sampling error variance formula also increased the accuracy of variance estimates for the multiplicative and Taylor Series procedures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Estimation accuracy of Thomas's likelihood-based procedure of meta-analysis: A Monte Carlo simulation.

Tested the accuracy of the likelihood-based validity generalization procedure proposed by H. Thomas (1990) for estimating the number of population correlations and their respective sizes and proportions in a mixed population. The simulation results showed that the Thomas procedure was highly accurate when there was only one correlation in the population. It was also accurate in estimating sizes and proportions of the population correlations when the correct number of population correlations was identified. However, its accuracy in estimating the actual number of population correlations decreased when they were close together and when the number of population correlations increased. The power of the procedure in identifying the existence of population correlations of magnitude zero and its accuracy in estimating means and standard deviations of population correlations are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Correction of ion source nonlinearities over a wide signal range in continuous-flow isotope ratio mass spectrometry of water-derived hydrogen

Ion source nonlinearities are characterized over a wide range of signal intensities characteristic of complex mixtures, and correction schemes are proposed and evaluated for high-precision determinations of D/H ratios from water via an on-line reduction system facilitating continuous-flow isotope ratio mass spectrometry. Hydrogen isotope ratios are shown to be sensitive to analyte pressure in the IRMS ion source with or without carrier gas admitted with analyte, indicating that analyte level must be taken into account for isotope ratio calculation. Two experimentally simple "peakwise" correction schemes, in which hydrogen isotope ratios are corrected after peak identification and ratio calculation, are compared to the method routinely applied to static dual-inlet IRMS measurements. It is demonstrated that traditional linear correction applied to continuous-flow peaks is adequate over small signal ranges, about m/z 2 +/- 0.5 V; however, a second order correction is required for acceptable accuracy and precision over larger ranges. In addition, tests of the peakwise algorithms were made using a set of liquid water samples with delta D Tap Water over the range of 39-407/1000 with uncorrected data with precisions of SD-(delta D Tap Water < 34/1000 and accuracy within 11/1000. Peakwise correction using a linear calibration model resulted in substantial improvements in precision (SD < 10/1000) and accuracy (< 4/1000). Peakwise-corrected data, calibrated using a second-order regression to account for unmatched detector response, are still further improved to accuracy within 2/1000 from the calibration curve. The peakwise correction schemes are advantageous because of experimental simplicity when applied to peaks of the same or similar shapes. This study shows that ion source non-linearities in hydrogen analysis require correction for optimal analytical performance and can successfully be handled using straightforward procedures over the wide signal range required for chromatographic analysis.     

Correction to Raju and Burke.

Reports an error in the article, "Two New Procedures for Studying Validity Generalization," by Nambury S. Raju and Michael J. Burke (Journal of Applied Psychology, Vol. 68, No. 3, pp 382-395). The equation in Step 4 for TSA 2 in Table 1 on page 385 was incorrectly stated; the correct formula is provided. (The following abstract of this article originally appeared in record 1983-31751-001) Several Monte Carlo studies examined the accuracy of 2 new procedures in estimating population true validity mean and variance. Results indicate that 1 of the new procedures provided slightly more accurate estimates than the procedures of F. L. Schmidt and J. E. Hunter (see record 1978-11448-001) and J. C. Callender and H. G. Osburn (see record 1981-00257-001). From a practical point of view, however, the estimates from the various procedures were quite comparable. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Frameless stereotactic lesion contour-guided surgery using a computer-navigated microscope

BACKGROUND: The Zeiss MKM System is a recently developed computerized operating microscope for image-guided neurosurgery. The clinical advantages, reliability, accuracy, and limitations of this technique were investigated. METHODS: Since February 1995, 78 consecutive frameless stereotactic image-guided procedures were performed in 73 patients (30 males, 43 females; mean age, 46.9 years; range, 16-77 years) for tumor surgery (50/64.1%), cavernoma removal (16/20.5%), and functional procedures (12/15.4%). Skin markers (74 cases) or bone markers (4 cases) and a standard imaging protocol (2-mm cranial computed tomography (CCT) in 59 cases/1.5-mm magnetic resonance imaging (MRI) in 19 cases) were used. RESULTS: The main advantages were pre-operative skin incision, craniotomy and corticotomy planning, and determination of lesion boundaries. Useful registration and system reliability were noted in 97% (76/78) of the procedures. A significant improvement in registration accuracy was observed over the test period from a mean of 4.8 mm (SD = 3.36; Cases 1-25) to a mean of 2.2 mm (SD = 0.86; Cases 26-78). This resulted in an improvement in application accuracy from <5 mm in 71% (Cases 1-25) to <2 mm in 95% (Cases 26-78) of cases, and the accuracy led to successful localization of the lesion in every case. Accuracy was reliable at the beginning of every procedure, but degraded to values >5 mm by the end of the procedure in 29% (22/78) of cases. MRI cases achieved higher application accuracy values (2.1 mm mean) than CT cases (3.7 mm mean). CONCLUSIONS: The system offers a reliable alternative to frame-assisted stereotactic craniotomies in lesion targeting, but would need an intraoperative image update for resection guidance.     

Interactive image directed neurosurgery: patient registration employing the Laitinen stereo-adapter

Fiducial markers visible on both imaging scans and the patient are a convenient and accurate method to register the patients head in stereotactic space preceeding an interactive image directed neurosurgical procedure. We have been using the Laitinen non-invasive relocatable stereo-adapter to carry the fidcucial markers both during the imaging and patient registration process. Since the adapter can be accurately remounted the surgical procedure can take place at any time interval after the imaging study. To compare registration accuracy studies were performed using a phantom carrying both surface fiducial markers and fiducial markers mounted on the stereo adapter. We have found that total system accuracy using either surface or adapter mounted markers and an optical tracking system is in the range of 3-5 mm and is acceptable for a broad range of neurosurgical applications.     

A note on the economic utility of generalized validity coefficients in personnel selection.

This study compared economic utility estimates that were based on noninteractive, interactive, independent multiplicative, and Taylor Series Approximation (TSA) 1 and 2 validity generalization results for clerical selection procedures at a large international manufacturing company. On the basis of estimates of the mean true validity and lower bound 90% credibility value, magnitude and percentage differences in resulting utility estimates across validity generalization procedures were relatively small for almost all comparisons. Regardless of the specific validity generalization parameter estimate used in estimating a utility value, the change in economic utility, going from the organization's current selection procedure (i.e., a verbal ability test) to an alternative procedure, was sizable in most cases. These results clearly demonstrate the practical similarity in utility terms of alternative validity generalization procedure results as well as the sizable economic value of minimum-level generalized validity coefficients. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Correction for variance restriction in point-biserial correlations.

A correction procedure is proposed for adjusting point-biserial correlations for attenuation produced by inopportune splits in the dichotomous variable. The correction procedure permits estimation of the point-biserial correlation that would have been seen had equal proportions been present. Monte Carlo simulation evidence is provided for the accuracy of the correction procedure. Also, an example is provided from the employee turnover literature to illustrate how the correction procedure may be used. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Correcting for indirect range restriction in meta-analysis: Testing a new meta-analytic procedure.

Using computer simulation, the authors assessed the accuracy of J. E. Hunter, F. L. Schmidt, and H. Le's (2006) procedure for correcting for indirect range restriction, the most common type of range restriction, in comparison with the conventional practice of applying the Thorndike Case II correction for direct range restriction. Hunter et al.'s procedure produced more accurate estimates of both the mean and standard deviation in meta-analysis than the conventional procedure. Even when its key assumption that the effect of selection on a 3rd variable is fully mediated by the independent variable was violated, Hunter et al.'s procedure was still relatively more accurate than the conventional procedure. When applied to data from a previously published meta-analysis, the new procedure yielded results that led to different substantive conclusions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An appraisal of the accuracy of Littmann's method of determining the real dimension of a retinal object

Estimation of the neuroretinal rim area in absolute units is becoming increasingly desirable in the evaluation of optic discs of glaucoma suspects. There are various methods of optic disc biometry, photogrammetric techniques being the most commonly reported. Any method of estimation of the real dimension of a retinal object must consider magnification due to the patient's eye. Photogrammetric techniques use Littmann's method extensively in this respect, assuming that it is an accurate way of performing the necessary correction. The accuracy of Littmann's method has not yet been assessed in a physiological setting. This study has found that, when the normal distributions of the optical elements eye are considered, in estimating the neuroretinal rim area, the method is at least 86% accurate (95% confidence interval) within an ametropia range -4 to +4 dioptres. This level of accuracy should be considered when drawing conclusions from any study in which Littmann's method is used.     

Overall job satisfaction: How good are single-item measures?

A meta-analysis of single-item measures of overall job satisfaction (28 correlations from 17 studies with 7,682 people) found an average uncorrected correlation of .63 (SD?=?.09) with scale measures of overall job satisfaction. The overall mean correlation (corrected only for reliability) is .67 (SD?=?.08), and it is moderated by the type of measurement scale used. The mean corrected correlation for the best group of scale measures ( 8 correlations, 1,735 people) is .72 (SD?=?.05). The correction for attenuation formula was used to estimate the minimum level of reliability for a single-item measure. These estimates range from .45 to .69, depending on the assumptions made. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rapid serum gentamicin assay by enzymatic adenylation

An improved, rapid and accurate enzymatic adenylation assay for gentamicin has been developed. It can be completed in one hour with an accuracy of +/- 2.7% (+/- 1 SD) for the range of gentamicin concentrations of 6-12 microgram/ml. Concentrated enzyme was used to prepare a complete adenylation mixture, which was stored frozen in aliquots suitable for daily assays. A special apparatus designed for efficient washing of phosphocellulose disks was used in the assay.     

Nonlinear Analysis of Ordinary Bridges Crossing Fault-Rupture Zones

Rooted in structural dynamics theory, three approximate procedures for estimating seismic demands for bridges crossing fault-rupture zones and deforming into their inelastic range are presented: modal pushover analysis (MPA), linear dynamic analysis, and linear static analysis. These procedures estimate the total seismic demand by superposing peak values of quasi-static and dynamic parts. The peak quasi-static demand in all three procedures is computed by nonlinear static analysis of the bridge subjected to peak values of all support displacements applied simultaneously. In the MPA and the linear dynamic analysis procedures, the peak dynamic demand is estimated by nonlinear static (or pushover) analysis and linear static analysis, respectively, for forces corresponding to the most-dominant mode. In the linear static analysis procedure, the peak dynamic demand is estimated by linear static analysis of the bridge due to lateral forces appropriate for bridges crossing fault-rupture zones. The three approximate procedures are shown to provide estimates of seismic demands that are accurate enough to be useful for practical applications. The linear static analysis procedure, which is much simpler than the other two approximate procedures, is recommended for practical analysis of “ordinary” bridges because it eliminates the need for mode shapes and vibration periods of the bridge.     

The theory, feasibility and accuracy of an ultrasonic method of estimating fetal weight

We present the theory, method, feasibility and accuracy of estimating fetal weight by measuring the fetal volume using compound ultrasonic scanning. The two parameters had a very high coefficient of correlation (0-9794), and the standard error in one series of 20 patients was only +/- 106 g. The correlation coefficient achieved by one of us who was new to ultrasound techniques was 0-82, which compared favourably with correlations between fetal weight and biparietal diameter measurements (r = 0-26). A discussion as to the correction factors required to allow for the unknown value of the velocity of ultrasound in fetal tissues, the clinical use of this method, and the possible means by which the accuracy of estimating fetal weight may be further improved is included.     

Refinements in validity generalization methods: Implications for the situational specificity hypothesis.

Using a large database, this study examined 3 refinements of validity generalization procedures: (1) a more accurate procedure for correcting the residual standard deviation (SD) for range restriction to estimate SDp, (2) use of r? instead of study-observed rs in the formula for sampling error variance, and (3) removal of non-Pearson rs. The 1st procedure does not affect the amount of variance accounted for by artifacts. The addition of the 2nd and 3rd procedures increased the mean percentage of validity variance accounted for by artifacts from 70 to 82%, a 17% increase. The cumulative addition of all 3 procedures decreased the mean SDp estimate from .150 to .106, a 29% decrease. Six additional variance-producing artifacts were identified that could not be corrected for. In light of these it was concluded that the obtained estimates of mean SDp and mean validity variance accounted for were consistent with the hypothesis that the true mean SDp value is close to zero. These findings provide further evidence against the situational specificity hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The restriction of range problem and nonignorable selection processes.

We describe a general model for estimating test validity when criterion scores cannot be observed for all cases. Unlike the traditional restriction of range correction formula, the proposed procedure can yield accurate estimates in problems in which an unobservable variable, related to y, is the basis for selection. This type of selection process is referred to as being nonignorable. In the nonignorable case, the regression statistics computed in the selected group, as well as the correction formula estimate, will be biased. The potential advantages of the proposed procedure over the correction formula approach are demonstrated in terms of hypothetical data sets in which the selection process is nonignorable. The shortcomings of the proposed analysis and future research needs are also discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Nickel content of human palatine tonsils: analysis of small tissue samples by flameless atomic absorption spectrophotometry

We describe a method for determining the nickel content of small tissue samples by flameless atomic absorption spectrophotometry in this case biopsy specimens from human palatine tonsils. Contact between tissue samples and metallic objects was avoided, except for the use of biopsy forceps (Type No. 8150.00 Wolf, stainless steel) for collecting samples, to imitate the actual procedure when small biopsy specimens are removed from the nasal mucosal membranes in nickel workers for histopathological and chemical investigations. Nickel contamination from this instrument was insignificant at the precision of the present procedures. The mean concentration of nickel in 15 tonsils was 13.5 +/- 7.0 (SD) microng/100g (wet wt). The mean nickel concentration in eight different samples of the same tonsil was 5.6 +/- 2.7 (SD microng/100 g.     

Clustering estimates of effect magnitude from independent studies.

One method of combining results of a series of studies is to calculate the average of the estimates of effect magnitude obtained from each study. The average estimate of effect magnitude may be misleading, however, when all studies do not share a common effect-magnitude parameter. When the effect-magnitude parameters (correlation coefficients or standardized mean differences) are heterogeneous across studies, it is often desirable to cluster studies into groups that are homogeneous with respect to the effect-size parameter. The present paper presents 2 procedures for clustering correlation coefficients and standardized mean differences when each estimator is based on the same number of observations. One procedure yields disjoint clusters and the other yields possibly overlapping clusters. In each case a method for determining the statistical significance level of the clusterings is given. Preliminary tests of homogeneity of a set of correlations or standardized mean differences are also given. The accuracy of the significance levels when estimators are based on different sample sizes is also studied. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Two new procedures for studying validity generalization.

Several Monte Carlo studies examined the accuracy of 2 new procedures in estimating population true validity mean and variance. Results indicate that 1 of the new procedures provided slightly more accurate estimates than the procedures of F. L. Schmidt and J. E. Hunter (see record 1978-11448-001) and J. C. Callender and H. G. Osburn (see record 1981-00257-001). From a practical point of view, however, the estimates from the various procedures were quite comparable. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)