Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Analysis of Variance”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 1,459 records · Page 81Linked to original sources
PubMed1995

Effects of quadriceps femoris muscle strengthening on crouch gait in children with spastic diplegia.

BACKGROUND AND PURPOSE: Despite evidence of weakness in children with cerebral palsy, the use of strength training in this population remains controversial. SUBJECTS: Fourteen children with spastic diplegia, ranging in age from 6 to 14 years (X = 9.1, SD = 2.5), participated in a bilateral quadriceps femoris muscle strengthening program. METHODS: The children exercised three times per week for 6 weeks using ankle weights at loads of approximately 65% of each child's maximum isotonic force production. The maximal voluntary contraction of the quadriceps femoris muscles was measured before, at the midpoint of, and immediately following the exercise program at 30, 60, and 90 degrees of knee flexion. Gait analyses were performed before and after the strengthening program to determine whether quadriceps femoris muscle strengthening influenced gait. RESULTS: Children with spastic diplegia can increase quadriceps femoris muscle strength through heavy resistance exercise. Repeated-measures analysis of variance and multivariate analysis of variance procedures were used to assess changes in force and in gait variables. Improvement in the degree of crouch at initial floor contact at the freely selected speed and an increase in stride length at free and fast speeds were found. CONCLUSION AND DISCUSSION: These findings suggest that resistance exercise is an effective treatment strategy and as such should be considered as one component in the habilitation of children with cerebral palsy.

Adolescent↗
PubMed1999

A generalized rank-order method for nonparametric analysis of data from exercise science: a tutorial.

Frequent violations of the assumption that data are normally distributed occur in exercise science and other life and behavioral sciences. When this assumption is violated, parametric statistical analyses may be inappropriate for data analysis. We provide a rationale for using a generalized form of nonparametric analyses based on the Puri and Sen (1985) L treated as a chi 2 approximation. If data do not meet the assumption of normality, this nonparametric approach has substantial power and is easy to use. An advantage of this generalized technique is that ranked data may be used in standard parametric statistical programs widely available on desktop and mainframe computers, for example, regression, analysis of variance (ANOVA), multivariate analysis of variance (MANOVA) within BioMed, SAS, SPSS. Once the data are ranked and analyzed with these programs, the only adjustment required is to use a standard formula to calculate the nonparametric test statistic, L, instead of the parametric test statistic (e.g., F). Thus, rank-order nonparametric models become parallel with their parametric counterparts allowing the researcher to select between them based on characteristics of the data distribution. Examples of this approach are provided using data from exercise science for regression, ANOVA (including repeated measures) and MANOVA techniques from SPSSPC. Using these procedures, researchers can easily examine data distributions and make an appropriate decision about parametric or nonparametric analyses while continuing to use their regular statistical packages.

Analysis of Variance↗
PubMed1997

Outcomes of inpatients treated on a VA psychiatric unit and a substance abuse treatment unit.

OBJECTIVE: The utility of the Treatment Outcome Profile (TOP) for measuring the effectiveness of acute inpatient psychiatric and substance abuse treatment was tested, including its internal reliability, validity, and sensitivity to treatment gains. The relationship between patients' satisfaction with services and treatment gains in quality of life, symptoms, and level of functioning was explored. METHODS: A pre-post research design was used with consecutive admissions to an inpatient psychiatric unit (N = 66) and a substance abuse treatment unit (N = 88) at a VA medical center. At admission and at discharge, the TOP, a self-report instrument assessing quality of life, symptoms, level of functioning, and patient satisfaction with services (at discharge only) was completed. Multivariate analysis of variance and univariate analysis of variance were used to test differences in scores between admission and discharge. RESULTS: Patients demonstrated significant treatment gains. Overall, compared with patients on the substance abuse unit, those receiving psychiatric treatment were more impaired at admission and had lower levels of self-reported therapeutic gain at discharge. Improvement for both groups occurred in quality of life, symptoms, and level of functioning. Both groups reported high levels of patient satisfaction, comparable with levels in other service industries. A high positive correlation (alpha = .61) was found between patient satisfaction and overall self-reported treatment gain. CONCLUSIONS: The results indicate that it is important to compare treatment effectiveness as well as costs when seeking less costly alternatives to inpatient care. The TOP is a valid and sensitive outcome measurement tool. Patient satisfaction is an important outcome variable and positively related to treatment gains in quality of life, symptoms, and level of functioning.

Analysis of Variance↗
PubMed2001

Towards non-invasive screening of skin lesions by near-infrared spectroscopy.

A noninvasive tool for skin tumor diagnosis would be a useful clinical adjunct. The purpose of this study was to determine whether near-infrared spectroscopy can be used to noninvasively characterize skin lesions. In vivo visible- and near-infrared spectra (400--2500 nm) of skin neoplasms (actinic keratoses, basal cell carcinomas, banal common acquired melanocytic nevi, dysplastic melanocytic nevi, actinic lentigines, and seborrheic keratoses) were collected by placing a fiberoptic probe on the skin. Paired t tests, repeated measures analysis of variance and linear discriminant analysis were used to determine whether significant spectral differences existed and whether spectra could be classified according to lesion type. Paired t tests showed significant differences (p < 0.05) between normal skin and skin lesions in several areas of the near-infrared spectrum. In addition, significant differences were found between the lesion groups by analysis of variance. Linear discriminant analysis classified spectra from benign lesions compared with premalignant or malignant lesions with high accuracy. Near-infrared spectroscopy is a promising noninvasive technique for the screening of skin lesions.

Analysis of Variance↗
PubMed2005

Erythrocyte zinc protoporphyrin is elevated with prematurity and fetal hypoxemia.

OBJECTIVE: To examine the utility of red blood cell (RBC) zinc protoporphyrin/heme ratio (ZnPP/H) as an indicator of fetal iron status, because unfavorable neurodevelopmental outcomes have been associated with poor iron status at birth, as indicated by low serum ferritin, and because few reliable indicators of fetal and early neonatal iron status exist. METHODS: Consecutively studied preterm and term fetuses at delivery included the following groups: (1) control nonhypoxic, (2) fetuses with intrauterine growth retardation (IUGR), and (3) fetuses of insulin-treated mothers (FDM). We hypothesized (1) that rapid growth velocity associated with an accelerated erythropoiesis among normal fetuses will lead to reduced iron delivery to a rapidly expanding RBC mass and higher umbilical cord blood RBC ZnPP/H and (2) that fetuses that are exposed to pathologic hypoxemia will experience an additional increase in erythropoiesis and higher cord ZnPP/H. ZnPP/H was determined on saline-washed cord blood erythrocytes by hematofluorometry and was examined for its relationship with clinical factors and cord blood laboratory measurements indicative of tissue oxygenation (plasma erythropoietin [EPO] and reticulocyte count) and iron status (plasma ferritin and erythrocyte indices). Statistical testing included 1-way analysis of variance, 2-way analysis of variance with covariates, simple linear regression, and multiple regression analysis. RESULTS: Among control group subjects, gestational age at birth was inversely correlated with RBC ZnPP/H and reticulocyte count and positively correlated with ferritin and EPO. Relative to control subjects, IUGR and FDM fetuses at specified gestational age groupings had higher ZnPP/H, lower plasma ferritin, and higher plasma EPO. Statistical modeling of the relationship between ZnPP/H and plasma ferritin among all study groups demonstrated significant impacts of gestational age, plasma EPO, maternal hypertension, and maternal smoking. CONCLUSIONS: The inverse association of fetal ZnPP/H with gestational age at birth among control subjects is attributable to erythropoietic stimulation likely as a result of increasing growth velocity at the earliest gestational ages. The relatively higher ZnPP/H observed among fetuses in the IUGR and FDM groups likely is attributable to increased erythropoietic activity secondary to pathologic hypoxemia. Decreased placental iron transfer may also have limited iron availability and contributed to elevated ZnPP/H in the IUGR group. These data support the concept that increased erythropoietic activity and/or limited iron transport may place infants of diabetic mothers and infants with growth retardation at risk for developing systemic iron deficiency later in infancy and in early childhood.

Erythrocyte Indices↗
PubMed1993

Analysis of partial variance (APV) as a statistical approach to control day to day variation in immune assays.

The considerable day to day variability in some immunologic assays can obscure relationships among measures of interest and thereby complicate interpretation of findings when effect sizes are modest. Analysis of partial variance (APV) is a technique that utilizes data obtained from controls run in the laboratory on the day of each assay to control for day to day variance statistically. The application of this technique to permit detection of otherwise obscured effects for both larger and smaller samples is exemplified utilizing data from two studies in which subjects were assessed on multiple different dates. These included a study of the association of depression with in vitro immune measures in 296 adolescents and a longitudinal study of 20 spouses of patients admitted to a cardiac intensive care unit studied together with 20 matched controls. APV was most useful in analyses of mitogen-induced lymphocyte proliferation assays, which had considerable day to day variability. In general, multivariate studies with functional immune measures may benefit most from application of this technique.

Adolescent↗
PubMed2005

Whole-genome variance components linkage analysis using single-nucleotide polymorphisms versus microsatellites on quantitative traits of derived phenotypes from factor analysis of electroencephalogram waves.

Alcohol dependence is a serious public health problem. We studied data from families participating in the Collaborative Study on the Genetics of Alcoholism (COGA) and made available to participants in the Genetic Analysis Workshop 14 (GAW14) in order to search for genes predisposing to alcohol dependence. Using factor analysis, we identified four factors (F1, F2, F3, F4) related to the electroencephalogram traits. We conducted variance components linkage analysis with each of the factors. Our results using the Affymetrix single-nucleotide polymorphism dataset showed significant evidence for a novel linkage of F3 (factor comprised of the three midline channel EEG measures from the target case of the Visual Oddball experiment ttdt2, 3, 4) to chromosome 18 (LOD = 3.45). This finding was confirmed by analyses of the microsatellite data (LOD = 2.73) and Illumina SNP data (LOD = 3.30). We also demonstrated that, in a sample like the COGA data, a dense single-nucleotide polymorphism map provides better linkage signals than low-resolution microsatellite map with quantitative traits.

Chromosome Mapping↗
PubMed2004

Analysis of rhythmic variance--ANORVA. A new simple method for detecting rhythms in biological time series.

Cyclic variations of variables are ubiquitous in biomedical science. A number of methods for detecting rhythms have been developed, but they are often difficult to interpret. A simple procedure for detecting cyclic variations in biological time series and quantification of their probability is presented here. Analysis of rhythmic variance (ANORVA) is based on the premise that the variance in groups of data from rhythmic variables is low when a time distance of one period exists between the data entries. A detailed stepwise calculation is presented including data entry and preparation, variance calculating, and difference testing. An example for the application of the procedure is provided, and a real dataset of the number of papers published per day in January 2003 using selected keywords is compared to randomized datasets. Randomized datasets show no cyclic variations. The number of papers published daily, however, shows a clear and significant (p < 0.03) circaseptan (period of 7 days) rhythm, probably of social origin.

Analysis of Variance↗
PubMed1979

The use of a standardized battery of Luria's tests in the diagnosis of lateralized cerebral dysfunction.

The present study was designed to examine the capability of a standardized battery of Luria's qualitative neuropsychological techniques in discriminating between right, left and diffuse brain-injured subjects. A total of sixty medically confirmed brain-damaged subjects were equally divided among the three groups. Subjects were assigned to two groups (right, left) according to medically proven lateralized brain injury to either the right or left hemisphere in the absence of verifiable insult to the opposite hemisphere. A third group was also selected in which medical evidence confirmed damage to both hemispheres (diffuse group). All three groups were matched for age and education. All subjects were tested on a standardized version of 269 Luria's qualitative neuropsychological test items. The items were divided into 11 sections based upon Luria's theory of brain function. Each of the 11 sections plus a right and a left hemisphere scale as well as an overall impairment scale yielded 14 summary measures of performance representing several areas of neuropsychological ability and overall severity of brain dysfunction. Analysis of variance and discriminant analysis were used to compare the three groups on these 14 summary measures. Analysis of variance revealed on significant difference between the three groups on the Left scale with the left group performing poorest. Discriminant analysis predicted the status of 59 of 60 subjects correctly (98% hit rate). The implication of the lack of significant simple relationships (ANOVA) and the complex interrelationships found using the discriminant analysis were discussed in terms of the support these results provide for Luria's theory of brain function. The specific qualitative aspects of the test battery and their use in the diagnosis of lateralized brain injury were also discussed. Indications for future research were pointed out.

Brain Diseases↗
PubMed2002

Insight and work performance in schizophrenia.

Research has linked impaired insight in schizophrenia to poorer medication compliance and poorer treatment outcome. The current study attempts to replicate previous findings that impaired insight is related to deficits in work function. To examine this question, 121 participants with schizophrenia or schizoaffective disorder enrolled in vocational rehabilitation were classified as having unimpaired (N = 65), or impaired (N = 56) insight. Next, participants were assigned a work placement and their work performance assessed on the third, fifth, and seventh weeks of work by using the Work Behavior Inventory. Among the 85 participants who completed these weeks of work, a multivariate analysis of variance and subsequent analysis of variance showed participants with impaired insight had significantly poorer ratings of work quality, work habits, cooperativeness, and personal presentation. When measures of global intelligence and executive function were entered as covariates in individual analysis of covariance, groups differed on measures of cooperativeness and personal presentation. Implications for rehabilitation are discussed.

Adult↗
PubMed2004

Power of variance component linkage analysis-II. Discrete traits.

We determine the power of variance component linkage analysis in the case of discrete, dichotomous traits analyzed under a classical liability threshold model. For simplicity we consider randomly ascertained samples and an additive model of variation incorporating a qtl, residual additive genetic factors, and individual-specific random environmental effects. We derive an expression for the power of variance component linkage analysis in arbitrary relative pairs, and compare the power of discrete and quantitative trait linkage analysis in the specific case of sibpairs. The predicted sample sizes required in linkage analysis of sibpairs are confirmed by analysis of simulated data. Unlike the affected-sibpair method, the power of discrete trait variance component analysis increases with trait prevalence. The relative efficiency of a discrete trait for linkage analysis increases with population trait prevalence, but does not exceed about 40% and is typically much less.

Analysis of Variance↗
PubMedDate not supplied

Efficacy of 24-hour shifts: prepared or impaired? A prospective study.

BACKGROUND: The effect of duty duration on performances is unknown. In a prospective cohort study model using repeated measures, we evaluated the effect of shift length on a battery of neuropsychologic performance indicators using our flight program as the test site. METHODS: Flight nurses completing 24- and 12-hour shifts were tested on memory, attention, reasoning, motor, and speed measures. Ratings of stress, fatigue, sleep quality, and logged amount of work and sleep were evaluated from personal journals kept for this purpose. Data were analyzed by linear regression and repeated measures multivariate analysis of variance (MANOVA) and analysis of variance (ANOVA). Clinical significance was set at P < 0.05. RESULTS: Fifteen subjects completed the testing and evaluation process. Neuropsychologic testing demonstrated that performance was not predicted by shift length, time of shift (day versus night), amount or quality of sleep before or during shift, or fatigue ratings. Age, gender, and education did not mediate shift length/test performance relationships. Uninterrupted sleep, stress ratings, and number of flights per shift modestly reduced some test scores. Predictably, repeated testings resulted in practice effects that reduced analysis power. We found that 24-hour shifts per se do not result in a cognitive decline compared with 12-hour shifts. Inconsistent sleep, number of flights, and the stressfulness of flights may have greater impact.

Air Ambulances↗
PubMed1997

Lipids in serum of patients with malignant ovarian neoplasms.

OBJECTIVE: In numerous papers, different associations of serum lipids and lipoproteins with neoplastic diseases were found. The aim of our work was to find out associations between levels of 11 serum lipids, lipoproteins and ovarian cancer. METHODS: 25 healthy women and 25 patients with ovarian cancer underwent examinations. Uni- and multivariate analysis of variance and discrimination analysis were used to analyze our results. RESULTS: The analysis demonstrates that ovarian carcinoma is associated with a significant reduction of total cholesterol and its esters in serum and in high density lipoprotein fractions compared to controls. CONCLUSION: It could be shown that using multivariate analysis of variance it is possible to find the optimal set of serum lipid parameters, containing serum esterified cholesterol, serum total cholesterol and high density lipoproteins esterified cholesterol, to differentiate healthy persons from patients affected by ovarian cancer.

Adult↗
PubMed2007

Closed-form confidence intervals on measures of precision for an interlaboratory study.

Within the pharmaceutical industry it is common practice to transfer analytical methods from one laboratory to other laboratories. An experiment or interlaboratory study is performed to estimate the repeatability, the intermediate precision, and the reproducibility of the analytical method. These measures of precision are quantified by appropriate sums of variance components from an analysis of variance model describing the structure of the data. In the literature, several methods have been described for calculating approximate (closed-form) confidence intervals on sums of variance components, i.e., Welch, Satterthwaite, and modified large-sample (MLS). Comparisons between these methods have been performed for one-way and two-way classification analysis of variance models only. Interlaboratory studies though often need higher order classifications. Therefore, these methods for constructing confidence intervals are compared on the measures of precision from a specfic three-way classification analysis of variance model that is frequently used for method transfer studies. Using a simulation study, the coverage probability for these methods is evaluated in situations where variance components may be estimated negatively with the standard moment estimates and where either the standard moment estimates are adjusted to zero or remain unadjusted. The MLS method is superior to the other two methods in case the standard moment estimates are used. If the adjusted moment estimates are used, then the method of Satterthwaite performs similar to the MLS method for many settings of the variance components and sample sizes but much better for some particular settings. The method of Satterthwaite performs better than the method of Welch for all the selected settings of variance components and sample sizes, irrespective of the standard or adjusted moment estimates.

Analysis of Variance↗
PubMed2006

How does the perception of a lesion influence visual search strategy in mammogram reading?

RATIONALE AND OBJECTIVES: Radiologists do not decide whether to report or to dismiss a perceived finding based solely on the conspicuity of the finding itself, but rather, they compare the finding with selected areas of the background. In this article, we examined how the perception of a malignant mass changed the background sampling strategy of experienced mammographers when searching mammograms for breast cancer. We determined whether these changes were different for correctly reported masses and for both visually inspected but unreported masses (ie, misses) and for lesion-free areas that were interpreted as containing a malignant mass (ie, false-positive decisions). MATERIALS AND METHODS: Four experienced mammographers read a case set of 20 two-view mammograms on two trials. Fifteen cases contained one biopsy-proven malignant mass, and five cases were lesion-free. Each cancer case had two sets of images: 1) the ones in which the lesion was reported at mammography screening, and 2) the first prior mammogram. On each trial, for each cancer case, only one set of images was shown to the observer in a balanced mix of current and prior cases per trial. The complementary set was shown in the next trial. The lesion-free cases were shown in both trials. The observers' eye positions were recorded. Spatial frequency analysis was used to represent the observers' background sampling strategy, and analysis of variance and correlation analysis were used to evaluate whether there were significant differences in the background areas sampled before and after the observers' eyes hit for the first time the location of the lesion. RESULTS: We found statistically significant differences (analysis of variance F(1,19) = 12.812, P = .0003) in the spatial frequency representation of the background areas sampled before and after the observers' eyes first hit the location of a true malignant mass. There were no statistically significant differences in the spatial frequency representation of background areas sampled before and after the observers' eyes first hit the location of a correctly reported malignant mass, but there were significant differences when either the observer did not report the mass (a miss) or the observer reported a lesion-free area as containing a mass (a false positive). CONCLUSION: A true malignant mass that the observers correctly report may be perceived immediately after image onset, thus biasing background sampling from the start, whereas areas that yield both false-negative and false-positive decisions may only be perceived during visual examination of the parenchyma. For the false negatives, our data suggest that after fixating the location of the lesion, the observers actively tried to reconcile the perception of the lesion with its background, whereas for the false positives, which represent a "true" lesion for the observers, background sampling was clearly different before and after the location was fixated for the first time. Hence, the perception of a finding effectively biases any further analysis of the case.

Breast Neoplasms↗
PubMed2006

Teamwork in the operating room: frontline perspectives among hospitals and operating room personnel.

BACKGROUND: The Joint Commission on Accreditation of Healthcare Organizations is proposing that hospitals measure culture beginning in 2007. However, a reliable and widely used measurement tool for the operating room (OR) setting does not currently exist. METHODS: OR personnel in 60 US hospitals were surveyed using the Safety Attitudes Questionnaire. The teamwork climate domain of the survey uses six items about difficulty speaking up, conflict resolution, physician-nurse collaboration, feeling supported by others, asking questions, and heeding nurse input. To justify grouping individual-level responses to a single score at each hospital OR level, the authors used a multilevel confirmatory factor analysis, intraclass correlations, within-group interrater reliability, and Cronbach's alpha. To detect differences at the hospital OR level and by caregiver type, the authors used multivariate analysis of variance (items) and analysis of variance (scale). RESULTS: The response rate was 77.1%. There was robust evidence for grouping individual-level respondents to the hospital OR level using the diverse set of statistical tests, e.g., Comparative Fit Index = 0.99, root mean squared error of approximation = 0.05, and acceptable intraclasss correlations, within-group interrater reliability values, and Cronbach's alpha = 0.79. Teamwork climate differed significantly by hospital (F59, 1,911 = 4.06, P < 0.001) and OR caregiver type (F4, 1,911 = 9.96, P < 0.001). CONCLUSIONS: Rigorous assessment of teamwork climate is possible using this psychometrically sound teamwork climate scale. This tool and initial benchmarks allow others to compare their teamwork climate to national means, in an effort to focus more on what excellent surgical teams do well.

Anesthesiology↗
PubMed2005

Molecular diversity of local Norwegian meadow fescue (Festuca pratensis Huds.) populations and Nordic cultivars-consequences for management and utilisation.

Genetic diversity and relatedness were studied in 30 Norwegian local populations of meadow fescue (Festuca pratensis Huds.) using amplified fragment length polymorphism (AFLP) markers. The populations were also compared with 13 Nordic meadow fescue cultivars in order to analyse the distribution of variation in local populations and cultivars and to elucidate relationships between local populations and cultivars. Analysis of molecular variance (AMOVA: ) analysis showed that most of the variation was present within populations and that little variation was found between local populations and cultivars. Separate AMOVA: analyses of local populations and cultivars revealed a higher level of variation within registered cultivars than within local populations. A cluster analysis based on corrected average pairwise differences between populations showed that the populations could be divided into three clusters, of which one also contained the cultivars. These results were supported by principal coordinates analysis. The results indicate that the Norwegian meadow fescue has a narrow genetic basis and that the local populations in Norway can be divided into three groups following the most probable routes of introduction of the species into Norway. The inland populations are closely related to the cultivars and have most probably been established as a result of migration from sown meadows. The western and southern populations probably originate from human activity-for example, trade-to the coastal western and northern parts of the country and to the central parts of southern Norway.

Analysis of Variance↗
PubMed2004

The repeatability of the 24-hour pad test.

A prospective observational study was conducted in a tertiary urogynaecology unit in women with the primary symptom of urinary incontinence to assess the repeatability of the 24-hour pad test. One hundred and eight women undertook seven 24-hour pad tests over 7 consecutive days together with 7 simultaneous fluid and activity charts. The results were analysed collectively and according to urodynamic subsets. Repeatability was assessed by repeated measures analysis of variance and univariate analysis of variance for each urodynamic diagnosis group (USI, mixed and no USI). Variation between pad test weights over the 7 days was low, supporting good repeatability. The number of days of pad testing required to approximate the 7-day average was 3 days. However, a single 24-hour pad test correlated highly with the 7-day average (r=0.881) and was considered sufficient to gauge leakage severity.

Aged↗