Statistical F-test Research Articles

Urinary excretion of sulfate and glucuronate conjugates in a free living population of adult males.

The measured levels of urinary conjugates of sulfate and of glucuronic acid in each subject were compared. Additionally, the potential influence of several dietary and nondietary factors upon conjugate excretion was evaluated using the statistical F-test

Statistical study of the liquefaction of an Indonesian subbituminous coal

Experiments using two level full factorial design were carried out to elucidate the importance of qualitative variables (the nature of gas phase, solvent type and catalyst) and quantitative variables (temperature, initial total pressure and contact time) upon liquefaction of an Indonesian subbituminous coal under short contact time conditions. To determine the significance of the effects, the statistical F-test with 99% confidence limits was used. It is shown that within the experimental ranges examined, the variables of highest significance for both coal conversion and oil yield are the nature of gas phase, solvent type and catalyst.

Multiple-taper spectral analysis of terrestrial free oscillations: part II

In Part I of this paper, we derived a set of data tapers designed to minimize the spectral leakage of decaying sinusoids immersed in white noise. Multiplying a long-period seismic record by K of these tapers creates K time series. A decaying sinusoid is fit to these K time series in the frequency domain at a number of chosen frequencies by a least-squares procedure. The fit is tested at each frequency using a statistical F-test. In Part I, we demonstrated that the multiple-taper method is a more sensitive detector of decaying sinusoids than the conventional direct spectral-estimate. In this paper, we present a number of extensions to the multiple-taper method. We explain how the technique can be modified to estimate the harmonic components of records containing gaps. We discuss how sinusoids at frequencies between FFT bin frequencies can be detected, and how this method can be combined with conventional multi-station stacking procedures.

Multiple-taper spectral analysis of terrestrial free oscillations: part I

We present a new method for estimating the frequencies of the Earth's free oscillations. This method is an extension of the techniques of Thomson (1982) for finding the harmonic components of a time series. Optimal tapers for reducing the spectral leakage of decaying sinusoids immersed in white noise are derived. Multiplying the data by the best K tapers creates K time series. A decaying sinusoid model is fit to the K time series by a least squares procedure. A statistical F-test is performed to test the fit of the decaying sinusoid model, and thus determine the probability that there are coherent oscillations in the data. The F-test is performed at a number of chosen frequencies, producing a measure of the certainty that there is a decaying sinusoid at each frequency. We compare this method with the conventional technique employing a discrete Fourier transform of a cosine-tapered time-series. The multiple-taper method is found to be a more sensitive detector of decaying sinusoids in a time series contaminated by white noise.

Room-temperature luminescence analysis of drugs with application to the Toxi-Lab drug identification system.

A method of analyzing drugs on the Toxi-Lab thin-layer chromatographic system by solid substrate room-temperature luminescence is described. Three pairs of unresolved drugs: quinine/cimetidine, caffeine/chlordiazepoxide, and phenazopyridine/lidocaine, were studied as model compounds. Their luminescence characteristics were obtained and calibration curves were found to be linear over two orders of magnitude. The effect of the nonluminescent component of each pair on the determination of the luminescent component was found to be negligible. Statistical F-tests showed that the observed differences in the slopes and intercepts of the calibration curves were due to random errors. The method was evaluated by determining quinine in urine samples at the ng level.

The problem of the determination of the structure of the compact part of the electrical double layer in the case of organic electrosoprtion in the light of consistency tests of experimental data

A new approach to obtain information about the surface solution structure and interfacial model has been presented. The approach allows us to investigate more effectively the electrosorption phenomena and to collect more detailed and relevant solution structure data. Four models of surface solution have been examined by means of the fitting of theoretical excess electrochemical Gibbs energy of mixing equations to experimental data. The statistical F-test served as a base for the critical evaluation of the acceptance or rejection of the investigated model. It has been shown that two models based on the local concentration concept i.e. Wilson's model and nonrandom two liquid or NRTL model can equally well describe the properties of the system under consideration at the specified conditions. Additionally the consistency test has been presented to verify derived conclusions. For the NRL model the surface pressure equation and the adsoprtion isotherm equation have also been derived.