SEARCH · PubMed Health

Results for “cross-validation”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 433 records · Page 24Linked to original sources

PubMed1989

Lung volume and spirometric standards for healthy female lifetime nonsmokers.

The FRC, RV, VC, TLC, RV/TLC (%), FVC, FEV1.0, FEF25-75%, and FEV1.0/FVC (%) were measured in 161 South Australian females aged 18.4-81.2 yr using a Stead-Wells spirometer and helium analyzer. Multiple regression equations were generated to predict these lung volume and spirometric parameters from the best weighted combination of age, mass, standing height, and various other anthropometric variables (FRC: R = 0.715, SEE = 387 ml; RV: R = 0.684, SEE = 256 ml; VC: R = 0.815, SEE = 383 ml; TLC: R = 0.754, SEE = 468 ml; RV/TLC: R = 0.780, SEE = 4.2%; FVC: R = 0.839, SEE = 375 ml; FEV1.0: R = 0.869, SEE = 326 ml; FEV1.0/FVC: R = 0.644, SEE = 5.7%; FEF25-75%: R = 0.753, SEE = 802 ml/s). The range of normality for the lung volumes was defined as the predicted value plus or minus the 95% confidence interval (two-tailed test), and the lower limit of normality for the spirometric variables was designated as the predicted value minus the 95% confidence interval (one-tailed test). Cross-validation of other equations in the literature indicates that they are of limited use for the sample and instrumentation used in this study.

Adult↗

PubMed1989

Validity and intertester error of anthropometric estimations of body density.

The purposes of this study were to evaluate the intertester error in anthropometry and its effect on estimations of actual body density (ABD), as well as to assess the validity of predicted body density (PBD) from selected anthropometric equation. Sixteen adult males X +/- SD = 21.98 +/- 1.65 years) volunteered to be measured by three experienced and reliable testers at eight circumference, two diameter, and eight skinfold sites as well as by underwater weighing. Eighteen commonly used anthropometric equations which predict body density were selected for evaluation. Repeated measures ANOVA with Tukey post-hoc comparisons were used to determine differences between testers for each anthropometric measure and the PBD values, as well as between the PBD values and ABD. There were significant (p less than 0.01) differences between testers for all anthropometric measures except bi-iliac diameter and hips circumference. However, the magnitude of the differences between testers were considered to be quite small and of no practical concern. There were significant differences among the PBD values and ABD for all equations except the base 10 logarithmic transformations of Durnin and Womersley. Seven of the equations, however, resulted in a constant error of less than or equal to 0.0085 g.ml-1. Overall, there was no single anthropometric equation which satisfied all of the cross-validation criteria suggested by previous investigators, however the linear equation of Forsyth and Sinning which included the scapular and abdominal skinfolds, as well as the bitrochanteric diameter resulted in an extremely small constant error (0.0024 g.ml-1) and an appropriate standard deviation of the PBD values (0.0127 g.ml-1).

Adult↗

PubMedDate not supplied

Measurement of quality-of-life changes in patients with Alzheimer's disease.

A scale was developed that appears to be a reliable and sensitive indicator of differences and changes in the quality of life of patients with Alzheimer's disease (AD) as the disease progresses. The instrument was generated from interviews with spouses and/or caregivers of AD patients, and was designed to be completed easily by the caregiver. The bipolar analog scale was based on the daily behavior of AD patients and was developed in three steps involving interviews with caregivers (step I), testing of questionnaires, and validation of the instrument. At step II, four iterative trials, each with a different version of the questionnaire, were performed for validation. The final form of the Progressive Deterioration Scale (PDS) contained 27 quality-of-life factors and was cross-validated in a second, separate study. The Global Deterioration Scale (GDS) for cognitive function was used as the external criterion for the analysis of the quality-of-life scales. Statistical analysis indicates that the PDS provides a reliable, valid, and sensitive measure of changes in the quality of life as AD progresses. The PDS achieved 80% overall accuracy in discriminating non-AD elderly patients from patients in the early, middle, and late stages of AD. This scale may provide a useful means for clinical evaluation (phase III) of potential medications to alleviate the symptoms of AD.

Aged↗

PubMed1989

Sex determination with the head of the radius.

Analysis of a sample of 1108 radii corresponding to 567 black and white North Americans in the Terry Collection at the Smithsonian Institution demonstrates that the diameter of the radial head is an accurate sex discriminator for human remains. A simple "radial-head method" of sex determination consists of measuring the maximum and minimum diameters of the head and comparing such measurements with the test cutoff points. The subject is female when the maximum radial head diameter (either left or right) is less than or equal to 21 mm, and male when the maximum diameter (either left or right) is greater than or equal to 24 mm. The same decisions apply to the minimum diameters of 20 mm or less and 23 mm or more, respectively. When the maximum diameter is 23 mm or the minimum is 22 mm, the subject is more likely male; when the maximum diameter is 22 mm or the minimum is 21 mm, the subject is more likely female. The sample frequency of any one of these latter diameters is never more than 16%. Cross-validation of the method with a sample of 50 pairs of radii of the Terry Collection, different from the original specimens, resulted in 92% sexing accuracy when using the left radius singly, 94% accuracy when using the right radius singly, and 96% accuracy when using both radii jointly.

Anthropology, Physical↗

PubMed1987

Prediction of neuroleptic-induced dystonia.

For patients receiving neuroleptics, age, sex, neuroleptic potency, and dose all influence the likelihood of a dystonic reaction. Little is known, however, of the relative importance of these factors or of the feasibility of predicting dystonia in individual patients. We reviewed 135 charts of psychotic inpatients to examine these factors and their usefulness in predicting dystonia. Age, sex, neuroleptic type, dose, and occurrence of dystonia were recorded for the first 4 days of drug treatment and were used to construct a linear discriminant function that classified the cases as to whether dystonia was expected. Internal cross-validation was performed, and the error rate of this classification procedure was calculated. Forty-nine (36%) of the patients had dystonia. A younger age was the most powerful predictor of dystonia. Male gender was second in predictive power with minor effects from neuroleptic dose and potency. The overall error rate (false-positive and false-negative errors combined) of the discriminant function was 30%. These results suggest the possibility of predicting dystonia in individual patients but should be regarded with caution since the predictive procedure has not been tested prospectively. If confirmed, these data may allow treatment strategies that protect patients from dystonia while sparing patients not at risk unnecessary treatment with antiparkinson agents.

Adolescent↗

PubMed1988

Empirical classification of infant-mother relationships from interactive behavior and crying during reunion.

Multiple discriminant function analysis (MDFA) was conducted with data from 255 Strange Situations conducted and scored by Ainsworth and her colleagues. Cross-validated discriminant functions and classification weights were obtained, allowing attachment classifications (A, B, C) to be assigned directly from scores on interactive behavior and crying during reunion episodes. In the past, classification agreement within laboratories has often been used as a training criterion. Unfortunately, this does not insure that classification criteria agreed upon within a laboratory are comparable across laboratories, nor does it insure that agreed upon criteria will yield the same classifications that would have been assigned by the researchers who developed the scoring system. The present results enable researchers who have mastered the scoring systems for reunion behavior and crying to obtain attachment classifications directly from scores on these variables. Alternatively, this procedure may be used to guide the training of, and validate classification decisions by, local judges.

Crying↗

PubMed1988

Discriminant analysis of laboratory tests in patients admitted to a coronary care unit.

Discriminant analysis of chemistry and hematology laboratory test results was used to classify patients with and without myocardial infarction in a coronary care unit. We studied 64 patients with myocardial infarction and 70 patients without infarction, using logistic regression, linear and quadratic discriminant analyses on untransformed and logarithmically transformed data. Serum aspartate aminotransferase (AST, EC 2.6.1.1), the best single discriminating test, classified 73% of patients correctly. Quadratic discriminant analysis on log-transformed data had a 98.5% classification accuracy when all variables were used in the discriminant function and had the highest classification accuracy and precision. All of the discriminant methods had acceptable cross-validation.

Adult↗

PubMed1988

Factor structure of the Arthritis Helplessness Index.

The factor structure of the Arthritis Helplessness Index (AHI) was examined using principal components factor analysis with varimax rotation. Data for the initial factor analysis came from a longitudinal study of 368 patients with rheumatoid arthritis (RA). Two slightly negatively correlated (r = -0.21) subscales emerged: internality and helplessness. This analysis was cross-validated twice. Findings reveal that the 2 subscales of the AHI are more reliable and valid than the total score. The 5 item helplessness subscale, in particular, appears to be a highly valid indicator of the degree to which patients with RA feel overwhelmed by their disease.

Arthritis↗

PubMed1988

Deconvolution of episodic hormone data: an analysis of the role of season on the onset of puberty in cows.

A new approach to the analysis of episodic hormone data is described. The method involves a stochastic model in which measured blood hormone concentration is represented as a convolution of individual pulses, each of which is thought of as the response to a burst of neural activity. Individual pulses are not constrained to occur in a fixed regular pattern in time. The methodology takes a series of blood hormone measurements and produces a spike train of pulse peak times together with a set of pulse shape parameters. This decomposition motivates some fresh approaches to the analysis of hormone data. For a given number of pulses the model is fit by minimizing a residual sum of squares criterion. This is a difficult combinatorial optimization problem. A randomized local adjustment algorithm is developed. Generalized cross-validation is used to select the number of pulses. The technique seems to produce reliable results on simulated data sets. The methodology is used to study some data concerned with the role of season of birth on the onset of puberty in bovine females. The analysis raises some interesting questions related to the maturation of the pituitary and hypothalamus.

Algorithms↗

PubMed1987

Assessment of PIC and MMPI scales in adolescent psychosis: a caution.

This study investigated the sensitivity of two frequently used multidimensional instruments--the Personality Inventory for Children (PIC) and the Minnesota Multiphasic Personality Inventory (MMPI)--in assessing psychotic states in adolescents. This issue arose as a result of the fact that the PSY scale on the PIC was constructed and cross-validated only on samples of children between the ages of 5 and 12 years. T-score comparisons between psychotic and nonpsychotic samples were performed, as well as Pearson correlations between PIC Psychosis (PSY) and MMPI Schizophrenia (Sc) scale T-scores. T-score comparisons indicated no significant differences between the groups on either PSY or Sc. A nonsignificant relationship between PSY and Sc scale elevations was also found. These results suggest the need for a profile-analytic approach to PIC and MMPI interpretation in identifying psychotic symptomatology in adolescents rather than PSY or Sc T-score elevation in isolation.

Adolescent↗

PubMed1987

Estimation of VO2max from a one-mile track walk, gender, age, and body weight.

The purpose of this investigation was to explore an alternative field test to estimate maximal oxygen consumption (VO2max) using a one-mile walk test. VO2max was determined in 343 healthy adult (males = 165, females = 178) subjects 30 to 69 yr using a treadmill protocol (mean +/- SD: VO2max = 37.0 +/- 10.7 ml X kg-1 X min-1). Each subject performed a minimum of two, one-mile track walks as fast as possible. The two fastest walks (T1, T2) with elapsed times within 30 s were used for subsequent analyses. Heart rates were monitored continuously and recorded every one-quarter mile. Multiple regression analysis (best sub-sets) to estimate VO2max (l X min-1) yielded the following predictor variables: track walk-1 time (T1); fourth quarter heart rate for track walk-1 (HR 1-4); age (yr); weight (lb); and sex (1 = male, 0 = female). The best equation (N = 174) was: VO2max = 6.9652 + (0.0091*WT) - (0.0257*AGE) + (0.5955*SEX) - (0.2240*T1) - (0.0115*HR1-4); r = 0.93, SEE = 0.325 l X min-1. Comparing observed and estimated VO2max values in a cross-validation group (N = 169) resulted in r = 0.92, SEE = 0.355 l X min-1. Generalized and sex-specific equations to estimate VO2max (ml X kg-1 X min-1) were also generated. The accuracy of estimation as expressed by SEE was similar among the equations. The results indicate that this one-mile walk test protocol provides a valid sub-maximum assessment for VO2max estimation.

Adult↗

PubMed1987

The use of the logistic model in space motion sickness prediction.

The one-equation and the two-equation logistic models were used to predict tested subjects' susceptibility to motion sickness in KC-135 parabolic flights using data from other ground-based motion sickness tests. A data set containing data from 6 provocative tests, 2 vestibular function tests, and 1 motion sickness experience questionnaire from 162 subjects was used in this study. The prediction results from the logistic models were compared with those from the previously-used Bayes linear discriminant analysis procedures. The results based on this data set show that the logistic models correctly predicted substantially more cases (an average of 13%) in the data subset used for model building. In the data subset used for model cross-validation, the logistic models correctly predicted 4% and 5% more cases in the prediction of vomit or nonvomit, and of degree of susceptibility, respectively. Overall, the logistic models ranged from 53 to 65% predictions of the three endpoint parameters, whereas the Bayes linear discriminant procedure ranged from 48 to 65% correct for the cross validation sample.

Adult↗

PubMed1987

Logistic risk model for the unique effects of inherent aerobic capacity on +Gz tolerance before and after simulated weightlessness.

Small sample size (n less than 10) and inappropriate analysis of multivariate data have hindered previous attempts to describe which physiologic and demographic variables are most important in determining how long humans can tolerate acceleration. Data from previous centrifuge studies conducted at NASA/Ames Research Center, utilizing a 7-14 d bed rest protocol to simulate weightlessness, were included in the current investigation. After review, data on 25 women and 22 men were available for analysis. Study variables included gender, age, weight, height, percent body fat, resting heart rate, mean arterial pressure, VO2max, and plasma volume. Since the dependent variable was time to greyout (failure), two contemporary biostatistical modeling procedures (proportional hazard and logistic discriminant function) were used to estimate risk, given a particular subject's profile. After adjusting for pre-bed-rest tolerance time, none of the profile variables remained in the risk equation for post-bed-rest tolerance greyout. However, prior to bed rest, risk of greyout could be predicted with 91% accuracy. All of the profile variables except weight, MAP, and those related to inherent aerobic capacity (VO2max, percent body fat, resting heart rate) entered the risk equation for pre-bed-rest greyout. A cross-validation using 24 new subjects indicated a very stable model for risk prediction, accurate within 5% of the original equation. The result for the inherent fitness variables is significant in that a consensus as to whether an increased aerobic capacity is beneficial or detrimental has not been satisfactorily established. We conclude that tolerance to +Gz acceleration before and after simulated weightlessness is independent of inherent aerobic fitness.

Acceleration↗

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↗