tailieunhanh - Quantitative Data Analysis: An Introduction

Magnetotelluric surveys (soundings) are a naturalsource electromagnetic (EM) geophysical method that utilizes variations in the Earth’s magnetic field to image subsurface structures. A magnetotelluric sounding was attempted at Weyburn but has not produced results. Consequently, a final assessment of its utility is not available (Monea et al., 2008). Electrical resistance tomography (ERT) is a technique of imaging subsurface electrical conductivity. When deployed in time-lapse mode, it is capable of detecting conductivity changes caused by the injection of CO2. The method utilizes borehole casings as electrodes for both stimulating electrical current in the ground and measuring the electrical potentials that are induced. ERT may be tested in Weyburn Phase II using a single borehole configuration as an. | GAO United States General Accounting Office Report to Program Evaluation and Methodology Division May 1992 Quantitative Data Analysis An Introduction GAO Preface GAO assists congressional decisionmakers in their deliberative process by furnishing analytical information on issues and options under consideration. Many diverse methodologies are needed to develop sound and timely answers to the questions that are posed by the Congress. To provide GAO evaluators with basic information about the more commonly used methodologies GAO s policy guidance includes documents such as methodology transfer papers and technical guidelines. This methodology transfer paper on quantitative data analysis deals with information expressed as numbers as opposed to words and is about statistical analysis in particular because most numerical analyses by GAO are of that form. The intended reader is the GAO generalist not statisticians and other experts on evaluation design and methodology. The paper aims to bridge the communications gap between generalist and specialist helping the generalist evaluator be a wiser consumer of technical advice and helping report reviewers be more sensitive to the potential for methodological errors. The intent is thus to provide a brief tour of the statistical terrain by introducing concepts and issues important to GAO s work illustrating the use of a variety of statistical methods discussing factors that influence the choice of methods and offering some advice on how to avoid pitfalls in the analysis of quantitative data. Concepts are presented in a nontechnical way by avoiding computational procedures except for a few illustrations and by avoiding a rigorous discussion of assumptions that underlie statistical methods. Quantitative Data Analysis is one of a series of papers issued by the Program Evaluation and Methodology Division PEMD . The purpose of the series is to provide GAO evaluators with guides to various Page 1 GAO .