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Results for “cross-validation”

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PubMed1992

Assessment of body composition in heart transplant patients.

Orthotopic heart transplantation (OHT) recipients often experience increased body weight (BW) following surgery. Using hydrostatic weighing (HW), this study assessed the body density (BD) and body composition of 17 white and seven black male OHT patients. It examined the cross-validity of the Jackson and Pollock seven and three site skinfold (SF) regression equations for predicting BD in these patients. We hypothesized that both prednisone (P) dose and months post-operative (MPO) would be inversely related to BD. The average of the last five of ten HW trials was used in computing BD. BW and % body fat (BF) were 88.5 +/- 17.8 kg (mean +/- SD) and 33.5 +/- 9.4%, respectively. The correlation coefficient between hydrostatically determined BD and BD determined via two of the three intercept revised Jackson and Pollock SF equations was r = 0.89, SE = 0.009. A polynomial regression model for BD using P dose and MPO provided a correlation coefficient of r = 0.71, SE = 0.015. Partial correlation techniques incorporating SF, age, MPO, and P dose indicated that neither P dose or MPO provided any significant additive effect, above SF and age, when predicting BD. We conclude that in OHT patients receiving glucocorticoids, the intercept revised Jackson and Pollock SF regression equations are generally applicable and associated with a SE of +/- 4 BF percentage points. Up to 49 months after OHT, both P dose and MPO are inversely related to BD but provide no additive value above SF for predicting BD.

Adult↗

PubMedDate not supplied

The Maternal Characteristics Scale: a cross validation.

A device for organizing practitioners' observations, the Maternal Characteristics Scale has successfully identified traits distinguishing samples of Caucasian neglectful mothers from nonneglectful. This cross-validation tested the scale with new and more diverse samples of both mothers and practitioners. Relatedness, impulse control, confidence, and verbal accessibility were again found to be associated with vulnerability to becoming neglectful. The scale appears to be a promising diagnostic and prognostic tool in the prevention and treatment of child neglect.

Child↗

PubMed1992

Evaluation of a neural-network classifier for PET scans of normal and Alzheimer's disease subjects.

The value of PET as an objective diagnostic tool for dementia may depend on the degree to which abnormal metabolic patterns can be detected by quantitative classification methods. In these studies, a neural-network classifier based on coarse region of interest analyses was used to classify normal and abnormal FDG-PET scans. The performance of neural networks and of an expert reader were evaluated by cross-validation testing. When the "abnormal" class was represented by subjects with clinical diagnoses of "Probable Alzheimer's," the areas under the relative-operating-characteristic (ROC) curves were 0.85 and 0.89 for the neural network and the expert reader, respectively. When testing with abnormal subjects represented by "Possible AD" cases, ROC areas for both the network and the expert were 0.81. The neural network out-performed discriminant analysis. It is concluded that PET has potential for the detection of abnormal brain function in dementing diseases, and that the combination of neural networks and PET is a useful diagnostic tool. Despite the low-resolution "view" afforded the neural network, its performance was nearly equivalent to that of an expert reader.

Adult↗

PubMed1992

A coupling procedure for the discrimination of mixed data.

A procedure is described for coupling different discriminators to a new (common) decision rule using the corresponding allocation vectors only. This enables one to cope jointly with data of different structure and/or scales of measurement but without strong restrictions on the number of (especially categorical) features. The method is combined with a consequent cross-validation process securing the results reached. Examples from medical diagnostics demonstrate the usefulness of the proposed procedure, especially in comparison with the known linear discriminant analysis as judged from the error rates obtained.

Diagnosis↗

PubMed1991

Relationships of structural dimensions to bench press strength in college males.

The purpose of this study was to determine the relationships between structural dimensions and bench press performance in college males. Members of required fitness classes (n = 170) were measured after 14 weeks of strength and aerobic endurance training. Anthropometric dimensions included upper arm and chest circumferences, upper and lower arm lengths, shoulder and hip widths, %fat, and height. Arm muscle cross-sectional area (CSA) was calculated from upper arm circumference corrected for triceps skinfold. Drop distance was measured from the bar to the pectoral muscles. Multiple regression analysis selected upper arm CSA, %fat, and chest circumference as the best items to predict bench press strength (R = 0.83; SEE = 11.6 kg). Cross-validation of the prediction equation on a similar sample (n = 89) produced an r = 0.74 between predicted and actual bench press (t = 0.53, p greater than 0.50). In a second cross validation sample (n = 57) who had trained more extensively with weights, the correlation between predicted and actual bench press was r = 0.57 (p less than 0.05). The prediction equations significantly (t = 6.59, p less than 0.01) underestimated bench press performance in the more extensively weight trained subjects. The results of this study suggest that bench press performance is related to structural dimensions in males and that extensive strength training may alter the relationship between size and strength.

Adult↗

PubMed1991

Predictors of long-term sexual assault trauma among a national sample of victimized college women.

Several multivariate studies have attempted to delineate the major predictors of long-term, sexual assault-induced aftereffects. The present study was an attempt to extend previous work by supplementing known preassault, assault, and postassault predictors of trauma with cognitive measures. The data were cross-sectional and included responses from 1,213 victims of sexual assault who were recruited from a national sample of higher education students. Utilizing hierarchical multiple regression analyses and a cross-validation procedure, the results suggested that the prior mental status of the victims, the forcefulness of the assaults, as well as two cognitive variables related to a victim's beliefs about sex and relationships predicted victims' scores on standardized measures of anxiety and depression. The relationships were such that the most traumatized victims were those women who had evidenced a history of mental health problems, who had experienced the more aggressive assaults, who tended to believe that people in relationships are not trustworthy, and tended to place conservative restrictions on the sexual acts and circumstances under which sex should occur. Taken together these variables accounted for between 9%-14% of the variance in sexual assault aftereffects. The discussion emphasizes the contribution of cognitive processes to the understanding of sexual assault trauma.

Adult↗

PubMed1991

Morphometry of the human thigh muscles. A comparison between anatomical sections and computer tomographic and magnetic resonance images.

The present study examined the relative accuracy and precision of MR and CT procedures for determining the CSA of individual muscles from the human thigh. Serial AN, CT and MR cross-sections were obtained from three cadaveric lower limbs. The MR measurements provided accurate and precise values for the CSAs of most thigh muscles, generally within +/- 7.5% of the AN standard. In contrast, CT tended systematically to overestimate the AN CSA by 10-20%. Retest procedures indicated that highly reliable measurements could be obtained from both MR and CT images. However, subjective interpretations of boundaries between closely apposed muscle bellies, particularly for muscles with more than one head, were necessary for resolving entities in the imaging records and this decreased the relative accuracy of MR and CT measures. Interestingly, MR records demonstrated an incomplete septum between vastus lateralis and vastus intermedius more prominently than AN cross-sections. The novel cross-validation procedures used in this study also highlighted several system-based errors in the MR records that, if undetected and left uncorrected, would have seriously biased the morphometric data obtained with this technique. In general, MR provides high resolution images of the human thigh muscles which may be used to obtain valid measures of the CSA of these structures.

Cadaver↗

PubMed1991

Midwest wrestling study: prediction of minimal weight for high school wrestlers.

This study determined the validity of previously published or newly derived equations to predict fat-free body mass (FFB) in high school wrestlers from the midwestern United States. Five laboratories participated in the data-pooling study (total sample of 860 subjects). Measures included body composition by underwater weighing and anthropometric measurements of body mass, stature, and selected circumferences, diameters, and skinfolds. Cross-validation of selected equations to predict FFB revealed the lowest levels of error from the equations of Lohman, Thorland et al., Katch and McArdle, and Behnke and Wilmore. Modification of the constants in these equations or generation of new equations did not substantially reduce prediction error. Overall, total error for these top equations ranged from 2.44 to 2.59 kg. However, based on observed trends, this error was of lower magnitude with the younger and lighter subjects and of higher magnitude with the older and heavier subjects. We conclude that these equations could be used singularly or collectively to determine FFB, and a minimal weight could then be derived and assigned to a scholastic wrestler.

Adolescent↗

PubMedDate not supplied

[Validity of 5 bioelectric impedance equations for the estimation of lean body mass in women].

Fat free mass (FFM) predicted by five bioelectrical impedance (BIA) available formulae (Segal et al., Lukaski et al., Kushner et al., Deurenberg et al., manufacturer's predictive equation) was compared with densitometrically-determined FFM (as a reference method) in two groups of young women with different anthropometric characteristics. In the farmers (very short and light individuals), none of the studied formulae was able to accurately predict FFM: this latter was overestimated in subjects with low and underestimated in those with high FFM. In the other group (INCAP employees), only values predicted by Lukaski formula were in perfect agreement with FFM, showing no bias depending on FFM changes. In conclusion, the available BIA formulae seem to be specific for population from which they were derived and could not be used on samples from other populations if not cross-validated.

Adolescent↗

PubMed1991

Modeling the cannabinoid receptor: a three-dimensional quantitative structure-activity analysis.

The structure-activity relationship studies that have been reported for cannabinoids suggest that 1) the conformation of the C-ring at the C9 position, 2) the A-ring phenolic hydroxyl, and 3) the hydrophobic side chain are important determinants for the production of analgesia, as well as other cannabinoid effects. However, either these previous structure-activity studies described for cannabinoid compounds have not been quantitative in nature or the prediction of the activity of known and unknown compounds based on molecular structure has not been tested in a comprehensive manner. In this study we describe a three-dimensional molecular modeling program using comparative molecular field analysis to derive quantitative structure-activity relationships fitting pharmacological potencies and binding affinities of cannabinoids. The analysis has proven to accurately fit the pharmacological activity of cannabinoid analogs, with cross-validated r2 values of greater than 0.3 and final analysis r2 values of greater than 0.88. Additionally, this study has further characterized the steric and electrostatic properties that account for the variations in their potency. The results from this study indicate that steric repulsion behind the C-ring is associated with decreased predicted binding affinity and pharmacological potency. On the other hand, the steric bulk of a side chain that is extended up to seven carbons contributes to predictions of increased binding affinity and potency. The electrostatic fields of cannabinoid analogs also contribute to the predicted in vitro and in vivo potencies. If the biological activities we have investigated are assumed to be the result of interaction with a single binding site, this method indicates the structural and physicochemical properties necessary for binding to the receptor and producing an effect. By defining cannabinoid binding affinity and behavioral activity pharmacophores, this method can be used for designing cannabinoid agonists and it is capable of predicting the activity of unknowns, thereby serving to facilitate rational drug design.

Animals↗

PubMed1991

The middle schooling process: influences on science and mathematics achievement from the longitudinal study of American youth.

The purpose of this longitudinal study was to develop and test a model of middle school science and mathematics achievement with a national probability sample of 3,116 seventh-grade public school students. Eighth-grade achievement was viewed as a function of readiness attributes on entry into seventh grade and intervening parent, peer, self, and classroom affective and behavioral measures. Data were collected from students and parents over three time periods in seventh and eighth grade. Results of a revised structural model showed that prior achievement in science and math was a strong mediator of effects in the process of schooling. Grades in sixth grade, parental expectations, parent educational attainment, and motivation had moderately strong indirect effects on eighth-grade achievements. Also notable was the positive direct influence of perceptions of classroom context on science and math achievement growth and the negative direct influence of sex (in favor of girls) on science achievement growth. Cross-validation on a split-half sample did not disconfirm the model. It was concluded that while prior achievement had a dominant influence in the schooling process, other variables including parental expectations, motivation, and classroom context do contribute to the schooling process and can be a focal point for improving school success. These and other factors, though helpful, may be most effective well before the middle school years.

Achievement↗

PubMed1990

Stress, health and performance in university students.

The hypothesis tested was that cognitive factors in the generation of stress, namely perceived coping incapacity (PCI), relate to the extent of psychosomatic ailments. We developed a new scale, CAST (Cognitive Appraisal Stress Test), with a 10 point self-rating of PCI using 16 questions on different aspects of perceived demands versus perceived capabilities. For the assessment of ailments relevant to stress we constructed a scale (PSYSOM) based on a translation of the Scheuch-Vogel symptom list (developed in the GDR from self-report of teachers who could not work as a result of work stress). A special scoring system combined duration, intensity and frequency of 30 symptoms and provided normalisation of distributions. The scales were administered on separate days to 75 female students in their second year (working to obtain admission to an honours degree course). The hypothesis was strongly supported, since the overall scale of PSYSOM correlated with CAST: r = 0.42, p less than .001. The physiologically defined subscale of 'skeletal muscle tension' correlated r = 0.65 with CAST. Subsequently CAST and PSYSOM have been shortened and factor analysed to give, in each case, a general principal component scale and several identifiable varimax subscales. Research using these scales on employees has now provided cross-validation of the first findings reported here.

Achievement↗

PubMed1990

Secondary structure prediction and protein design.

For non-homologous proteins, and after cross-validation, the methods reviewed in this article exhibit a probability index (percentage of correctly predicted residues per predicted residues) of 59-65.5% according to the methods employed with a standard deviation of 7% for three conformational states: alpha-helix, beta-strand and coil. These present limitations in the accuracy of prediction are related both to the limited number of known structures and to the effect of long-range interactions. The methods based on sequence similarity can improve the accuracy of prediction by expressing the homology of the protein to be predicted explicitly with proteins in the database. Under these circumstances, the probability index can reach 87% with a standard deviation of 6.6%. This property was used for modelling homologous proteins by assisting in amino acid sequence alignments. Examples will be given for the alignment of serine proteinases.

Amino Acid Sequence↗

PubMed1979

Individual temperament as a predictor of health or premature disease.

Two studies of temperament as a possible predictor of continuing good health or premature disease are reported. In earlier work to determine youthful precursors of premature disease, a number of separate characteristics distinguishing medical students who remain healthy from those with premature disorders have been identified. Characterization by temperament, an expression of innate biological endowment, provides a more global portrayal of an organism that can an aggregate of separate characteristics alone. Criteria for designating three temperament types, termed Alpha, Beta and Gamma, are presented. In 1948, 45 subjects were assigned to one of these types on the basis of youthful characteristics. The subjects in the three temperament groups had different health outcomes 30 years later, significant at the p less than 0.01 level. Gamma type had the most disorders and deaths, Beta type the fewest. A cross-validation study on 127 subjects had similar results at the p less than 0.05 level. Temperament appears to be a variable of predictive potential of individual stamina, or of vulnerability to premature disease and death.

Adult↗

PubMed1979

Prediction of maximal oxygen uptake in boys, ages 7-15 years.

Predictions of Vo2max (1 min-1 and ml kg-1 min-1) were obtained via multiple regression procedures from a sample of 100 boys, ages 6.7-14.8 years. Prediction equations for Vo2max (1 min-1) were obtained from the subjects' height, and the Vo2 (1 min-1) and heart rate observed during the third min of a treadmill walk (R = 0.95; CV = +/- 9.3%). A similar prediction was obtained when the subjects' age, height and weight were used (R = -0.94; CV = +/- 9.7%). Vo2max (ml kg-1 min-1) was predicted with similar accuracy (CV = +/- 8.4%) from age, and heart rate, VCO2(1 min-1), Vo2 (ml kg min-1), or from simply age, height and weight (CV = +/- 9.2%). Cross-validation of the equations with another sample of 39 boys demonstrated that the prediction equations based on laboratory data were quite stable, % errors approximately 1-2 +/- 9%. However, the equations based on age, height and weight underestimated the Vo2max slightly, both in 1 min (X = -0.091 min) and ml kg min (X = -2.2 ml kg min, P less than 0.05). The results indicate that reasonably reliable and accurate estimates of Vo2max for children may be obtained from either laboratory data, or simply from their age, height and weight.

Adolescent↗

PubMed1979

Alcoholism-related content in the MMPI: item analysis of alcoholics vs. normal and general psychiatric populations.

An analysis of alcoholism-related content in the MMPI was undertaken using an alcoholic population, a psychiatric population and two normal populations. The alcoholic and psychiatric groups were drawn from facilities in the Minneapolis-St. Paul area, and the normal populations were the Hathaway Adult Group and the Mayo Clinic nonpsychiatric patient group. A derivation study and a cross-validation resulted in the identification of three item pools: 1) that discriminate alcoholics from both normals and psychiatric patients, 2) items that discriminate alcoholics from normals only, 3) items that discriminate alcoholics from psychiatric patients only. Only seven items discriminate both male and female alcoholics from both normals and psychiatric patients. These items have substantial face validity. As the core of alcoholism-related content in the MMPI, they can serve as a stem for the development of scales with more specialized purposes.

Alcoholism↗

PubMed1978

Objective assessment of prior air traffic control-related experience through the use of an occupational knowledge test.

The Occupational Knowledge Test (OKT) 101-B was administered to 784 air traffic control trainees who entered the FAA Academy's 16-week training course in 1976. All trainees completed the nonradar laboratory portion of the training and, in addition, completed a preemployment questionnaire. Based on responses to the questionnaire, the trainees were assigned to one of three experience groups, corresponding to groups given credit for experience using Civil Service Commission (CSC) selection procedures. It was found that the OKT was highly correlated with experience (r = 0.64) and, in addition, had a higher correlation with successful completion of the nonradar lab than did experience (r = 0.25 vs. 0.12). It was determined that use of an OKT score of 75 or above to assign extra credit would result in a failure rate of 3.1% for those receiving credit, while use of the current experience scale would result in a failure rate of 7.6% for those receiving extra credit on the CSC selection battery. The results held up for a cross-validation sample of 432 trainees who entered the Academy during 1977. Based on the results, it is recommended that an OKT score of 75 or above be used to assign extra credit for experience in the selection of air traffic controllers.

Aviation↗

PubMedDate not supplied

Schooling, occupational motivation, and personality as related to success in paramedical training.

Measures of prior school experience, motivation for working in a health care job, and personality were evaluated as potential predictors of success in Navy paramedical training. When, by multiple regression procedures, years of school completed, numbers of suspensions or expulsions from school, occupational motivation, and Comrey personality scale scores were combined with an aptitude measure that is used for guiding recruits into paramedical training, the cross-validity for predicting training completion was significantly increased (P less than 0.001) from 0.40 to 0.50. Practical means for applying these measures to the screening of candidates for paramedical training were developed. Results of the evaluation suggest that guiding people into jobs that they neither prefer nor perceive as congruent with their abilities and interests can significantly reduce the chances for occupational success.

Achievement↗