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 163 records · Page 9Linked to original sources
PubMed1996

Biological evaluation of trace element data in human ovaries by statistical analysis.

Analysis of variance, analysis of covariance, correlation coefficient, multiple correlation, and partial correlation coefficient statistical tests were applied to Cs, Cr, Co, Fe, Rb, Sc, Se, and Zn content in human ovaries in order to evaluate statistically the possible relationships between these trace elements at: the ovary as an organ, each ovarian phase separately, each morphological part independent of the ovarian phase, and between cortex and medulla within the ovarian phases. The element Cs seems to have a homogeneous distribution between cortex and medulla within reproductive and menopausal phase. Zinc shows a trend to have an antagonistic relation with Cs, Cr, Co, and Fe during fetal and reproductive phases and not during menopausal phase. The relationship between Zn and Cs when Fe is kept constant could be used as a tool for the decontamination of the ovary from an abnormal Cs content or for the inhibition of the accumulation of the same element to the ovarian tissue.

Adult↗
PubMed1997

Trace elements, age, and sex in amyotrophic lateral sclerosis disease.

The statistical tests analysis of variance, analysis of covariance, correlation coefficient, Kolmogorov-Smirnov test, t-test, and Tukey test were applied to copper, magnesium, manganese, and zinc content in serum (S) and in cerebrospinal fluid (CSF) of controls and of a sporadic form of Amyotrophic Lateral Sclerosis (ALS) disease. This is carried out in order to evaluate statistically the possible relationships among the trace elements when ALS patients and controls are considered as independent groups, within sex groups and within age decades of both patients and control classes. A statistically significant difference between older controls (age > 40) and ALS patients (age > 40) for copper in CSF, copper in S, manganese in S, and zinc in CSF was found. Statistically significant correlation coefficients within the different classes formed for this study were observed. Within this pool, a correlation of patient group can differ statistically from the corresponding one of controls and vice versa. Thus, this correlation could be characteristic of the group from which is extracted, e.g., the correlation between copper in S and zinc in S, which is characteristic of ALS patients when considered as an independent group as well as members of the male patient class.

Adolescent↗
PubMed2004

Patterns of alcohol and substance use and abuse in persons with spinal cord injury: risk factors and correlates.

OBJECTIVE: To investigate patterns of alcohol consumption and abuse and substance use among persons with spinal cord injury (SCI), relating these patterns to demographic and injury-related characteristics, as well as to key medical and psychosocial outcomes. DESIGN: Retrospective cross-sectional. PARTICIPANTS: Subjects with traumatic SCI (N=3041) with dates of injury between June 6, 1975, and June 23, 2002, who were interviewed between November 2000 and March 2003. SETTING: Sixteen Model Spinal Cord Injury Systems participating in this collaborative study during the 2000-2005 grant cycle. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Alcohol consumption, substance use, CAGE questionnaire, Satisfaction With Life Scale, Craig Handicap Assessment Reporting Technique, and pain. Data were analyzed using chi-square tests, analysis of variance, analysis of covariance, and logistic regression models. RESULTS: Fourteen percent of the subjects were classified as likely to have an alcohol abuse issue, based on the CAGE, and 11% reported using illegal drugs or prescription medications for nonmedical reasons. Demographic and injury characteristics were associated with alcohol consumption patterns, abuse, and substance use. At-risk drinkers and substance users tended to be younger, single, male, and less educated. Those who were CAGE positive and substance users reported more pain and lower satisfaction with life. Persons who drank without indication of problem drinking had superior occupation outcomes. Pressure ulcers were associated with substance use. CONCLUSIONS: Alcohol abuse and substance use were related to a number of adverse outcomes. The specific role of drinking with increased work activity deserves further exploration.

Adolescent↗
PubMed2006

Nutrition knowledge is associated with greater weight loss in obese and overweight low-income mothers.

OBJECTIVE: To examine if greater nutrition knowledge vs gains in knowledge promote more successful weight loss in low-income, overweight and obese mothers with young children. DESIGN: A convenience sample of mothers and their children were measured for height and weight; mothers completed demographic and nutrition knowledge questionnaires pre- and post-intervention. SUBJECTS/SETTING: Participants (N=141) were recruited from government and public health clinics and elementary schools. Inclusion criteria for mothers were: family income <200% federal poverty level; overweight/obese; and Hispanic, African-American, or white race/ethnicity. INTERVENTION: Eight weekly weight-loss classes emphasizing diet, physical activity, and behavior modification based on Social Cognitive Theory were administered to mothers. MAIN OUTCOME MEASURES: Improvements in maternal nutrition knowledge and weight loss. STATISTICAL ANALYSES PERFORMED: Paired-samples t tests, repeated measures analysis of variance, analysis of covariance, Pearson correlations, and chi(2) statistics. RESULTS: Nutrition knowledge of mothers increased in all areas. Participants with weight loss > or =2.27 kg (responders) had greater knowledge than those who did not; however, the actual net gain was similar for those who lost and did not lose weight. Weight gainers only improved in two areas on the test, whereas weight-loss responders increased knowledge in all six. Responders appeared more cognizant of diet, weight loss, and health information. CONCLUSIONS: Weight-management programs should include a strong component of nutrition education to alleviate knowledge inequalities and promote more effective weight control. In low-income mothers, greater initial knowledge may be more predictive of weight loss than gains in knowledge during an intervention.

Adult↗
PubMedDate not supplied

Web-based intervention for changing attitudes of obesity among current and future teachers.

OBJECTIVE: To evaluate attitude change among student teachers and schoolteachers when exposed to a Web-based educational module promoting size acceptance. DESIGN: Subjects were randomly assigned to a control group or 1 of 4 treatment groups to evaluate the effect of module, presenter credibility, and/or image on attitudes of obesity and processes of change using the Elaboration Likelihood Model (ELM) testing cognitive and psychological cues. On-line assessment occurred at the pretest, posttest, and 6-week follow-up. SETTING: Web-based. PARTICIPANTS: 258 adults, mean age 26.8 +/- 10.2 years. INTERVENTION: Module content included factors related to obesity, implications of weight loss efforts, classroom activities, and bias-free intervention techniques. MAIN OUTCOME MEASURE(S): Attitudes of obesity by the Anti-Fat Attitudes Test and the effect of the presenter using a bipolar rating scale. ANALYSIS: One-way repeated measures analysis of variance, analysis of covariance, and general post hoc analysis. RESULTS: Negative attitudes decreased in treatment groups between pretest to posttest (P < .001) and pretest to follow-up (P < or = .006). Unlike the credible "nonfat" presenter, exposure to the credible "fat" presenter positively influenced attitude change (P = .031). CONCLUSIONS AND IMPLICATIONS: On-line communication of size acceptance improved attitudes of obesity long term. The findings support the ELM. The module demonstrates promise for teacher training in size sensitivity.

Adult↗
PubMed1996

Evaluation of the VA's Pilot Program in Institutional Reorganization toward Primary and Ambulatory Care: Part I, Changes in process and outcomes of care.

PURPOSE: To evaluate the impact of the reorganization of an academic Veterans Affairs medical center toward primary and ambulatory care--including the implementation of a medical-center-wide interdisciplinary firm system and ambulatory care training program--on the quality of primary ambulatory care. METHOD: Randomly selected male veterans visiting the Veterans Affairs Medical Center in Sepulveda, California, were surveyed in 1992, early in the implementation of the program, and in 1993, after the program had been fully implemented. Two surveys were used: one before the veterans saw their primary care providers (practice-based survey) and the other immediately after patient visits (visit-based survey). Survey-participant data were then linked to computerized utilization and mortality data. Survey topics were mapped to the medical center's strategic plan and goals for ambulatory care, and focused on patients' reports about the care they had received in terms of continuity, access, preventive care, and other aspects of the biopsychosocial model of care. Administrative computer data were then used to evaluate effects on medical center workload. Statistical analyses included analysis of variance, analysis of covariance, chi-square, and logistic regression. RESULTS: For practice-based comparisons, complete data were available for 1,262 veterans in 1992 and 1,373 in 1993. For visit-based comparisons, complete data were available for 1,407 veterans in 1992 and 643 in 1993. Results included statistically significant improvements in continuity of care and detection of depression as well as increased rates of preventive care counseling (smoking and exercise). The proportion of veterans reporting being seen by physicians increased, as did the proportion of patients seen for check-ups rather than for acute problems. Fewer patients were seen in subspecialty clinics than in general medicine clinics. Patient satisfaction increased, hospitalizations decreased, and death rates decreased. Alcohol counseling and access to care for acute symptoms declined. Workload shifted from subspecialists to generalists and from inpatient care to outpatient care. CONCLUSION: The institutional reorganization toward primary and ambulatory care succeeded in substantially improving the quality of ambulatory care, reflecting improvements in the system of care and of health care provider training in ambulatory care.

Ambulatory Care↗
PubMed2001

Comparison of wound healing using the CO2 laser at 10.6 microm and 9.55 microm.

OBJECTIVES/HYPOTHESIS: The wound healing characteristics of incisions made with the short pulsed CO2 laser tuned to 9.55 microm versus the traditional 10.6 microm were investigated. Previous studies have shown that at 9.55 microm, collagen is targeted more selectively than at 10.6 microm, which results in decreased acute thermal injury patterns. This study investigates the difference in wound healing over time between lasers and compares laser incisions with cold knife techniques. STUDY DESIGN: Randomized controlled trial using a porcine model. METHODS: Tissue from 10.6-microm and 9.55-microm incisions of 10 piglets was evaluated with histological analysis and tensiometry at 3, 7, 14, and 21 days postoperatively. A Bonferroni-Dunn corrected analysis of variance analysis at a 95% significance level was used to compare the effect of wavelength. RESULTS: The results demonstrate that although knife incisions are consistently stronger than laser incisions, the 9.55-microm CO2 laser incisions are no stronger than incisions made with the conventional 10.6-microm laser. Furthermore, histological analysis shows no difference in lateral thermal damage between lasers at 3, 7, 14, and 21 days postoperatively. The progression of collagen formation and inflammation does not differ over time. CONCLUSION: This study of wound healing using a porcine model demonstrates that the 9.55-microm CO2 laser does not demonstrate an improvement in wound healing over the traditional 10.6-microm CO2 laser. These results may be secondary to the common explosive vaporization mechanism produced by both lasers in the infrared spectrum.

Analysis of Variance↗
PubMed2004

Pregabalin add-on treatment: a randomized, double-blind, placebo-controlled, dose-response study in adults with partial seizures.

PURPOSE: To evaluate pregabalin (PGB), 150 mg/day, and PGB, 600 mg/day, as an add-on treatment for patients with refractory partial seizures concurrently treated with one to three anticonvulsants (AEDs). METHODS: An international (13 countries), multicenter (45 centers), 12-week, double-blind, randomized study in which patients with partial seizures received placebo (n = 96); PGB, 150 mg/day (n = 99); or PGB, 600 mg/day (n = 92); given 3 times a day (t.i.d.). The primary efficacy criterion was reduction in seizure frequency during treatment as compared with baseline, as measured by RRatio, the symmetrical percentage change in seizure rates determined from daily seizure diaries. The RRatio between the 8-week baseline (pretreatment phase) and the 12-week treatment period were compared between each of the PGB groups and the placebo group by using an analysis of variance analysis of the intent-to-treat population. RESULTS: PGB, 150 mg/day and 600 mg/day, were both significantly more effective than placebo in reducing the RRatio [-11.5 (p = 0.0007) and -31.4 (p < or = 0.0001), respectively, vs. 0.9]. These RRatio values correspond to seizure-frequency reductions from baseline of -1.8, 20.6, and 47.8% for placebo, 150 mg/day, and 600 mg/day, respectively. PGB efficacy was significantly dose related (p < or = 0.0001). Secondary efficacy variables corroborated the findings of the primary analysis. Significantly more patients were responders (> or =50% reduction in seizure frequency) in the PGB, 600 mg/day (43.5%), group than in the placebo group (6.2%) (p < or = 0.001). PGB was well tolerated. Dose-related, treatment-emergent adverse events (> or =10%), mostly mild or moderate in intensity, were somnolence, dizziness, ataxia, diplopia, and weight gain. The withdrawal rate due to adverse events was 10% of patients at 150 mg/day and 18.5% of patients at 600 mg/day, compared with 6.2% of patients receiving placebo. CONCLUSIONS: PGB, 150 mg/day and 600 mg/day, is highly effective and well-tolerated add-on therapy in patients with partial seizures.

Adolescent↗
PubMed2004

Surface roughness of packable composite resins polished with various systems.

PURPOSE: The aim of this study was to evaluate the surface roughness of four packable composite resins, SureFil (Dentsply, Petrópolis, Rio de Janeiro, Brazil), Prodigy Condensable (Kerr Co., Orange, CA, USA), Filtek P60 (3M do Brasil, São Paulo, Brazil), and ALERT (Jeneric/Pentron, Inc., Wallingford, CT, USA) and one microhybrid composite resin (Filtek Z250, 3M do Brasil) after polishing with four finishing systems. MATERIALS AND METHODS: Twenty specimens were made of each material (5 mm in diameter and 4 mm high) and were analyzed with a profilometer (Perthometer S8P, Perthen, Mahr, Germany) to measure the mean surface roughness (Ra). The specimens were then divided into four groups according to the polishing system: group 1--Sof-Lex (3M do Brasil), group 2--Enhance (Dentsply), group 3--Composite Finishing Kit (KG Sorensen, Barueri, São Paulo, Brazil), and group 4--Jiffy Polisher Cups (Ultradent Products, Inc., South Jordan, UT, USA). The specimens were polished and then evaluated for Ra, and the data were subjected to analysis of variance, analysis of covariance, and Tukey's test (p = .05). RESULTS: The mean Ra of SureFil polished with Sof-Lex was significantly lower than that of KG points. Prodigy Condensable polished with Enhance showed a significantly less rough surface than when polished with Sof-Lex. Filtek P60 did not exhibit a significant difference with the various polishing systems. For ALERT the lowest mean Ra was obtained with Sof-Lex and the highest mean Ra with KG points. Regarding Filtek Z250, polishing with KG and Jiffy points resulted in a significantly lower mean Ra than when polished with Enhance. CONCLUSIONS: Packable composite resins display variable roughness depending on the polishing system used; the Sof-Lex disks and Jiffy points resulted in the best Ra values for the majority of the materials tested. CLINICAL SIGNIFICANCE: The Sof-Lex disks and the Jiffy points produced the smoothest surfaces for the tested resin composites. As a result, they should be considered for clinical use as preferred polishing systems for these resin composites.

Analysis of Variance↗
PubMed2002

Relationship between implant preload and screw loosening on implant-supported prostheses.

The purpose of this study was to determine whether varying the preload on the implant-abutment complex would affect screw loosening under simulated loading conditions. Abutment screws in sample models were tightened to 25, 30, 35, and 40 N-cm. One group of samples was allowed to stand for 3 hours after being torqued and then loosened. Another group of samples was retorqued after 10 minutes with the same initial torque value and then allowed to stand for 3 hours before loosening. For the load group of samples, the abutments were torqued into place, retorqued after 10 minutes, and a load applied for 3 hours before loosening. Cyclic loading was carried out using a servo-hydraulic testing machine with the values cycled between 1 and 26 pounds and the load applied directly to the abutments. Analysis of variance, analysis of covariance, and linear regression analysis was performed. Within the parameters of this in vitro investigation, the following recommendations can be made: (1) retightening abutment screws 10 minutes after the initial torque applications should be routinely performed and (2) increasing the torque value for abutment screws above 30 N-cm can be beneficial for abutment-implant stability and to decrease screw loosening.

Analysis of Variance↗
PubMed1989

Juvenile diabetics' oral health and locus of control. A pilot study.

The purpose of this pilot study program was to evaluate the effects of a one-year dental health education program on the oral health status and locus of control of juvenile diabetic children. Thirty subjects with juvenile diabetes mellitus were allocated to control and experimental treatment groups so that group frequencies (age, sex, race, duration of diabetes) were similar. Both groups had a Silness and Loe Plaque Index (PLI) and a Ramfjord Periodontal Disease Index (PDI) performed, and received an oral prophylaxis three times over the one-year period. Locus of control was measured at baseline and one year using the Children's Health Locus of Control Scale. In addition, the experimental group received an extensive dental health education program which emphasized the effects of dental disease on diabetes control. Twenty-five subjects completed the study. Pre- and post-locus of control measures were analyzed using the Wilcoxon Matched Pairs Signed Rank test. The Mann Whitney U Test was used to analyze differences between the groups. Indexes were compared using nonparametric two-factor repeated measures analysis of variance. Analysis revealed no statistically significant differences between groups or in locus of control scores over time. However, PDI and PLI scores improved in both groups, particularly from baseline to six months (p less than .01). Although not statistically significant, both groups exhibited a high internal locus of control. While the dental health education program resulted in only minor improvements in mean group scores, the intervention of preventive treatment produced significant improvement in measured indexes.

Analysis of Variance↗
PubMed1993

Analysis of variance for 'component stripping' decomposition of multiexponential curves.

An extended analysis of variance is presented for a multiexponential curve fitting procedure, known as 'curve stripping', 'curve peeling', or 'successive subtraction'. In addition to the standard, single variable curves, this analysis includes the two dimensional multiexponential surface analysis. The calculations take into account features required by the graphical user interface that was specifically designed to facilitate the fitting process. The evaluation of the goodness of fit includes an F test (to evaluate the number of components needed to fit the data), and correlation coefficients (to evaluate individual parameters).

Algorithms↗
PubMed1998

[Analysis of variance of bacterial counts in milk. 1. Characterization of total variance and the components of variance random sampling error, methodologic error and variation between parallel errors during storage].

In contrast to the prevailing automatized chemical analytical methods, classical microbiological techniques are linked with considerable material- and human-dependent sources of errors. These effects must be objectively considered for assessing the reliability and representativeness of a test result. As an example for error analysis, the deviation of bacterial counts and the influence of the time of testing, bacterial species involved (total bacterial count, coliform count) and the detection method used (pour-/spread-plate) were determined in a repeated testing of parallel samples of pasteurized (stored for 8 days at 10 degrees C) and raw (stored for 3 days at 6 degrees C) milk. Separate characterization of deviation components, namely, unavoidable random sampling error as well as methodical error and variation between parallel samples, was made possible by means of a test design where variance analysis was applied. Based on the results of the study, the following conclusions can be drawn: 1. Immediately after filling, the total count deviation in milk mainly followed the POISSON-distribution model and allowed a reliable hygiene evaluation of lots even with few samples. Subsequently, regardless of the examination procedure used, the setting up of parallel dilution series can be disregarded. 2. With increasing storage period, bacterial multiplication especially of psychrotrophs leads to unpredictable changes in the bacterial profile and density. With the increase in errors between samples, it is common to find packages which have acceptable microbiological quality but are already spoiled by the time of the expiry date labeled. As a consequence, a uniform acceptance or rejection of the batch is seldom possible. 3. Because the contamination level of coliforms in certified raw milk mostly lies near the detection limit, coliform counts with high relative deviation are expected to be found in milk directly after filling. Since no bacterial multiplication takes place during storage, then error between samples always predominates the total variation. 4. The present results cannot be simply applied to other selective enumerations of microorganisms. Yet, a non-homogenous distribution should always be expected at microbial counts close to the detection limit. Technical errors arising from clustering as well as eugonic growth can additionally hamper the counting of colonies of such microorganisms. Effects of these observations in the decision-making process will be dealt with in the second communication.

Analysis of Variance↗
PubMed1998

Statistical approaches to determine analytical variability and specifications: application of experimental design and variance component analysis.

Assessment of analytical variability is recognized as an important factor for the establishment of specifications. Estimation of the variance for an analytical procedure can be accomplished using a variety of approaches. The approach of variance component analysis was applied retrospectively, as well as prospectively, to estimate analytical variance. The prospective approach also included the use of experimental design. Recent new drug substance examples illustrating these approaches are presented. In these examples, the analytical property of potency was evaluated. Factors examined in the experimental design include laboratory, day, analyst, instrument and column. Process variability can also be determined by variance component analysis. For a stable drug substance, combining the analytical and process variances provides an estimate on the total variance for the analytical property of potency. With the total variability statistically derived, an appropriate specification that is consistent with process and analytical capability can be established.

Analysis of Variance↗
PubMed2007

Separation of base allele and sampling term effects gives new insights in variance component QTL analysis.

BACKGROUND: Variance component (VC) models are commonly used for Quantitative Trait Loci (QTL) mapping in outbred populations. Here, the QTL effect is given as a random effect and a critical part of the model is the relationship between the phenotypic values and the random effect. In the traditional VC model, each individual has a unique QTL effect and the relationship between these random effects is given as a covariance structure (known as the identity-by-descent (IBD) matrix). RESULTS: We present an alternative notation of the variance component model, where the elements of the random effect are independent base generation allele effects and sampling term effects. The relationship between the phenotypic vales and the random effect is given by an incidence matrix, which results in a novel, but statistically equivalent, version of the traditional VC model. A general algorithm to estimate this incidence matrix is presented. Since the model is given in terms of base generation allele effects and sampling term effects, these effects can be estimated separately using best linear unbiased prediction (BLUP). From simulated data, we showed that biallelic QTL effects could be accurately clustered using the BLUP obtained from our model notation when markers are fully informative, and that the accuracy increased with the size of the QTL effect. We also developed a measure indicating whether a base generation marker homozygote is a QTL heterozygote or not, by comparing the variances of the sampling term BLUP and the base generation allele BLUP. A ratio greater than one gives strong support for a QTL heterozygote. CONCLUSION: We developed a simple presentation of the VC QTL model for identification of base generation allele effects in QTL linkage analysis. The base generation allele effects and sampling term effects were separated in our model notation. This clarifies the assumptions of the model and should also enhance the development of genome scan methods.

Alleles↗
PubMed1999

Why analysis of variance is inappropriate for multiclinic trials.

Violations of the assumptions behind analysis of variance (ANOVA) models do not tend to affect the alpha-level but can greatly decrease the power of a clinical trial to detect treatment effects. The very nature of multiclinic studies guarantees the violation of some of these assumptions. In this article, I explore the reduction in power that results from two of these violations--heterogeneity of variance across sites and the existence of "floor" and "ceiling" effects. I propose other methods of statistical analysis that avoid this loss of power.

Analysis of Variance↗
PubMed1993

Combined pedigree and twin family study to determine the sources of variation in serum biotinidase activity: the usefulness of multiple study designs.

Biotinidase, the enzyme responsible for recycling the vitamin biotin, is deficient in most individuals with late-onset multiple carboxylase deficiency. Based on clinical criteria, biotinidase deficiency appears to be inherited as an autosomal recessive trait; however, the inheritance of biotinidase serum activity as a quantitative trait has not been studied previously. In this study, both segregation analysis of proband families and the analysis of twin family data were used to determine the relative contributions of a major gene, polygenes and environment to the variation in serum biotinidase activity. Segregation analysis of 24 families of biotinidase-deficient individuals indicated that serum biotinidase activity is determined by the segregation of a single codominant major gene with the variability about the mean of each major genotype attributable to environmental effects. Significant polygenic effects could not be detected by this analysis. Variance component analysis of 128 twin families, which included the twins, their spouses, and their offspring, indicated that 70% of total variance in biotinidase activity is attributable to additive genetic effects, 22% to individual environmental effects, and 8% to shared environmental effects. The model also included an age effect for females. A portion (27%) of the estimated additive variance may be attributed to the segregation of the major gene. This study emphasizes the usefulness of studying multiple data sets representing different types of family relationships.

Amidohydrolases↗