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At least 703 records · Page 39Linked to original sources
PubMed1983

The precision of results from nonlinear regression analysis of data following a three-parameter one-exponential equation.

Simulated experimental data were generated from error-free data following the equation y = A - Be-kt where A, B, and k are constants and were analyzed by iterative nonlinear regression using one of two basic published computer programs. The effect of the simulated experimental error in y on the precision of the computed constants A, B, and k was evaluated. The errors were either independent of y (simple errors) or proportional to y (relative errors) and outliers were sometimes introduced. Other factors investigated were the number of data points per regression, the range of values of y, and the effect of weighting the data. The results show that the errors in the computed constants, and particularly the rate constant k, may be considerably magnified with respect to the errors in the experimental data. The quantitative relationships that are presented are useful aids in the design of biochemical experiments in which the above equation is applicable.

Computers↗
PubMed1976

An application of non-linear regression analysis to tests of liver function.

Serum samples from 42 cases of acute hepatitis were analysed for up to 10 tests of liver function. The results of these tests were then analysed by standard statistical methods. A curve fitting exercise was performed and regression coefficients and comparative data were calculated for each of six curve types, relating to each pair of liver function tests. The correlation coefficients found were then tested for significance. From the 216 correlation coefficients tested eleven were found to be highly significant (p less than 0.001) and of these, seven were of non-linear regression curves. Examples have been given of the use of regression equations in assessing the relative sensitivities of different tests at levels on the borderline of the normal range.

Acute Disease↗
PubMed2002

The curve of Spee and craniofacial morphology: a multiple regression analysis.

The aim of this study was to investigate the relationship between the curve of Spee and skeletal facial morphology. Dental casts and lateral cephalograms were obtained from 59 orthodontic patients. The amount of concavity of the curve of Spee was calculated by a second-order quadratic interpolation of buccal cusp tips obtained from lateral digital photographs of the teeth. The cephalometric analysis aimed to evaluate the sagittal and vertical craniofacial dimensions as well as the position of the mandibular condyle with respect to the occlusal plane. These variables, included in a multiple regression model, could explain 34% of the total variance of the curve of Spee. The amount of the curvature was significantly related to (a) the horizontal position of the condyle with respect to the dentition, (b) the sagittal position of the mandible with respect to the anterior cranial base, and (c) the ratio between the posterior and anterior facial height. No significant relationship was found between the curve of Spec and any of the other cephalometric variables. The curve of Spee was not influenced by age and gender of the subjects investigated.

Adolescent↗
PubMed2002

Is there a sex difference in the association between birth weight and systolic blood pressure in later life? Findings from a meta-regression analysis.

The aim of this study was to determine whether a sex difference exists in the association between birth weight and systolic blood pressure. A meta-analysis of all observational studies (n = 57) in which the study population contained both males and females and the association between birth weight and blood pressure was presented as a linear regression coefficient was undertaken. There were no differences in the pooled regression coefficients between males and females combining all studies; the regression of blood pressure on birth weight for males was -1.27 (95% confidence interval: -1.77, -0.77) mmHg/kg and for females was -1.24 (95% confidence interval: -1.90, -0.58) mmHg/kg. When studies in which blood pressure had been measured in childhood were considered separately from those in which it was measured in adulthood, there were no sex differences in either age group. The pooled regression coefficient tended to be weaker in studies reporting sex-specific results than in those reporting combined results. These findings suggest that reports of sex differences in the association between birth weight and blood pressure are chance findings.

Adult↗
PubMed1984

Regression analysis in physiological research: some comments on the problem of repeated measurements.

The statistical implications of repeated-measures linear regression, in which each subject contributes several pairs of measurements to the analysis, are discussed in the context of physiological research. The major point of the paper is that standard least-squares procedures cannot be applied without modification to regression problems with repeated measures. An example is given.

Adult↗
PubMed1990

Prognostic factors in resected stages I and II adenocarcinoma of the lung. A multivariate regression analysis of 137 consecutive patients.

The prognostic factors for survival after radical resection of stages I and II adenocarcinoma of the lung were investigated in 137 consecutive patients. Seventeen variables were investigated by use of Cox's multivariate regression model. Factors predicting a poor prognosis were low status of Karnofsky performance, histologic subtype of solid carcinoma with formation of mucus, and T2 and N1 disease. The staging according to American Joint Committee on Cancer Staging did not provide significant information on survival when the variables describing T and N status were included in the Cox model. The new international staging system carried prognostic information because the new stages I and II are identical with the N0 and N1 groups. Groupings of patients according to the prognostic variables defined in this study allow for more detailed prediction of survival than can be achieved solely by T and N groupings. The prognostic information may be used in the design and interpretation of clinical trials and in the selection of patients who might be considered potential candidates for studies of adjuvant treatment.

Adenocarcinoma↗
PubMed1993

t-REML for robust heteroscedastic regression analysis of mitochondrial power.

The paper reports a long series of observations on two statistically independent variates which have different nonlinear regressions on the same parameter vector. In our analysis of the data, heteroscedasticity is handled by residual maximum likelihood, REML, but to cope with outliers as well, REML based on a t-specification, called t-REML, is introduced. The data are the results of factorial experiments designed to model the quantitative performance of mitochondria generating aerobic power. The response variates are flux, measured as respiration, and ATP potential as log(ATP/ADP). The background of metabolism and oxidative phosphorylation is briefly sketched.

Adenosine Diphosphate↗
PubMed2003

What determines the costs of repair and rehabilitation of flexor tendon injuries in zone II? A multiple regression analysis of data from southern Sweden.

The epidemiology and costs of repair and rehabilitation of zone II flexor tendon injuries in 135 patients from the southern part of Sweden were analysed. The little finger was most frequently injured (43%), usually with a knife (46%), and 30% of the injuries were work related. Total median costs within the health-care sector for the injuries were SEK 48,500 (1 EURO=9.23 SEK, 4/1/2002). Costs in other sectors were SEK 93,000. Active mobilization or mobilization with rubber band traction increased costs within the health-care sector (SEK 7400 or SEK 6000, respectively) but improved range of movement (5-7%). Immobilization had a higher complication rate (rupture or need for secondary procedures), which in itself increased total costs by 57%. Non-linear effects were found between age and costs within the health-care sector and the outcome.

Accidents, Occupational↗