Estadística para Investigadores. Introducción al Diseño de Experimentos, Análisis de Datos y Construcción de Modelos

Source: OAI


Sumario: Comparación de dos tratamientos -- Comparación de más de dos tratamientos -- Midiendo los efectos de variables -- Construcción y empleo de modelos

17 Reads
    • "The calculation was based on the design matrix. Once the experiments were statistically ordered (STAT- GRAPHICS Plus), Yates algorithm [32] was employed to analyze the values of the output variable. It should be noted that the term significance or significant in statistics means probably true (not due to chance). "
    [Show abstract] [Hide abstract]
    ABSTRACT: This study reports a novel method of tailoring the properties of ZnO nanostructures by electrodeposition in presence of chemically-reduced graphene oxide (rGO). The coupled electrochemical and chemical reduction of graphene oxide resulted in few-layer graphene-based material. The presence of rGO in the electrolytic bath showed a marked influence on the morphology and structure of the hybrid nanostructures. The results indicated the presence of 5 mg L−1 rGO results in a 42.9% decrease in resistivity of the hybrid material with respect to the pure ZnO. The proposed approach shows very promising for the fabrication of transparent conductive oxide electrodes.
    No preview · Article · Aug 2014 · Ceramics International
    • "Two full factorial 2 3 experimental designs (Box 2000) were developed to evaluate the effect of the temperature (T), extraction duration/time (t) and solvent type (S) in the extracts from barks of young and old trees. Temperature values were 25°C and 35ºC, extraction duration time 1h and 12 h, and the solvents were acetone and ethanol from Merck (Darmstadt, Germany). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Pinus radiata barks obtained from tress of different ages, as subproduct of pulp and paper (trees less than 10 years) and sawmill (trees between 20 to 25 years) industries, were used to produce extracts containing phenolic compounds. A factorial design 2 3 was used to evaluate the influence of the variables temperature (25 – 35 ºC), solvent type (acetone -ethanol) and extraction time (1-12 h). The extracts were compared in their extraction yield (%), total phenols (by FolinCiocalteau), and radical scavenging activity (by DPPH). The extract obtained from old trunks presented a higher extraction yield than from young trees. The highest yield value was 2.56%, which was obtained using acetone as solvent for 12 h and 35°C. The highest concentration of phenol (5.84±0.18 g CE g extract -1), and scavenging activity (IP=86.1±4.4%) were also obtained for this type of extract. The extraction duration was the variable that most influenced the parameters studied. The bark's radical scavenging power was greater than BHT (40%) and slightly lower than ascorbic acid (92%), common commercial antioxidants.
    No preview · Article · Jun 2014 · Maderas: Ciencia y Tecnologia
  • Source
    • "In order to develop a selective and sensitive HRP based biosensor for LEV determination, the experimental variables that strongly affect to its chronoamperometric response were evaluated. Thus, applied potential (E ap ), pH and concentration of H 2 O 2 (C H 2 O 2 ) were evaluated by means of the experimental design methodology [18] [19]. The performance of the developed biosensors was checked in terms of reproducibility, repeatability and application to complex matrices, such as pharmaceutical drugs and spiked human plasma. "
    [Show abstract] [Hide abstract]
    ABSTRACT: This work shows an easy and fast electrochemical method for Levetiracetam (LEV) determination, which is a novel antiepileptic. Most of the methods used up to now for its determination required a pre-treatment of the sample. It is shown here that the developed Peroxidase based biosensors avoid this kind of drawbacks. Screen-printed carbon electrodes have been used as transducers for the Peroxidase immobilization by pyrrole electropolymerization. Experimental variables that can affect LEV chronoamperometric response, such as hydrogen peroxide concentration, pH and applied potential, have been optimized in order to perform a selective LEV determination. Under these conditions, the performance of the biosensors has been tested. The residual standard deviation (RSD) of the slopes of different calibration curves was 9.77% (n=4 and alpha=0.05) for the reproducibility and 7.73% (n=4 and alpha=0.05) in the case of the repeatability. An average limit of detection of 9.81x10(-6) M (alpha=beta=0.05) was obtained. The biosensors have been finally applied to the determination of LEV in complex matrices, such as pharmaceutical drugs and spiked human plasma samples, yielding successful results.
    Full-text · Article · Dec 2008 · Bioelectrochemistry (Amsterdam, Netherlands)
Show more