Thesis (M.S.)--Virginia Polytechnic Institute, 1952. / Vita. Includes bibliographical references (leaves 101-102). Also available via the Internet.

This thesis is a comparative study of optimal design-based univariate stratification as applied to highly skewed populations such as those observed in business and agricultural surveys. Optimal stratification is a widely used method for reducing the variance or cost of estimates, and this work considers various optimal stratification algorithms, and in particular optimal boundary algorithms, to support this objective. We first provide a background to the theory of stratification and stratified random sampling, and extend this through the derivation of optimal allocation strategies. We then examine the effect of allocation strategies on the variance and design effect of estimators, and in particular find several issues in applying optimal or Neyman allocation when there is little correlation between the survey population and auxiliary information. We present a derivation of the intractable equations for the construction of optimal stratum boundaries, based on the work of Dalenius (1950), and derive the cumulative square root of frequency approximation of Dalenius & Hodges (1957). We then note a number of issues within the implementation of the cumulative square root of frequency rule surrounding the construction of initial intervals, and find that the placement of boundaries and the variance of estimates can be affected by the number of initial intervals. This then leads us to propose two new extensions to the cumulative square root of frequency algorithm, using linear and spline interpolation, and we find that these result in some improvements in the results for this algorithm. We also present a complete derivation of the Ekman algorithm, and consider the extended approach of Hedlin (2000). We derive several new results relating to the Ekman algorithm, and propose a new kernel density based algorithm. We find all three Ekman based algorithms produce similar results for larger populations, and provide some recommendations on the use of these algorithms depending on the size of the population. We look at the derivation and implementation of the Lavallee-Hidiroglou algorithm, and find that it is often slow to converge or does not converge for Neyman allocation. We therefore adopt a random search model of Kozak (2004), and note that the Lavallee-Hidiroglou algorithm generally produces superior results across all populations used in this thesis. We briefly investigate the optimal number of strata by examining the work of Cochran (1977) and Kozak (2006), and find that there is a diminishing marginal effect from increasing the number of strata and possibly some benefit from constructing more than six strata. However we also acknowledge that the cost of constructing such strata may offset any potential gain in precision from constructing more than five or six strata. Finally we consider the how many of these problems can be developed further, and ultimately find that such problems for deciding the number of strata, construction of stratum boundaries, and the allocation of sample units among the strata may require an approach that takes account of the relationship between the auxiliary variable and the survey information. We therefore suggest investigating these algorithms further within the context of a model-assisted environment in order to help account for the relationship between the auxiliary information and survey population.

Although the minimum qualifications for election to the American Farmer Degree have remained essentially the same during the last ten years, the actual achievements the candidates for the American Farmer Degree have increased beyond these minimums. / Master of Science

Master of Science

This thesis presents a new perspective on the study of past farm success and failure; it builds on the concepts of resilience and vulnerability to construct a theoretical framework which integrates environmental, historical and ethnographical data. The basic framework establishes that the resilience or vulnerability of a social-ecological system is a function of three factors: i) the exposure of the system to external (environmental) stresses, ii) the sensitivity of the system to these stresses and iii) the ability of the human component of the system to respond to them. The research focused on the component of human capacity of response (the sum of coping and adaptive capacity) within this framework. The temporal scale of the study was the 18th century, although reference is made to earlier periods for comparison. The location of the study area was Mývatnssveit, a livestock-based farming community in northern Iceland, while the spatial scale of the study is that of individual farms in the area. The results showed that successful farms had a higher capacity of response than failed farms, and that this was conferred by a greater availability and quality of resources, including human resources, natural resources and productive resources (those directly involved in agriculture). Human resources were assessed by records of number of servants per farm and by evidence of learning/knowledge transfer obtained via micromorphological analyses of home-field soils. Natural resources considered to be of particular importance were fish and eggs. Indicators of productive resources included tax value, land rent, livestock numbers and phosphorus content in home-fields. The latter revealed that the soil condition pre-settlement was linked to its post-settlement quality. An analysis of present day perceptions of historical farm abandonment in the area corresponds with the conclusions reached through the data integration in placing the human factor above the environmental one in influencing success and failure. The thesis concludes by highlighting the individuality of the study farms and the historical resilience of the livestock-based farming system. Additionally, areas of potential for future research are identified.

This dissertation presents a case study of agricultural land use patterns and marketing aspects in the Taif region of Saudi Arabia. This area is one of importance to the overall agricultural future of Saudi Arabia, being a major producer of fruits, vegetables and dates in the Kingdom. In recent years, increases in personal income associated with oil production in the Kingdom have created significant changes in the types of crops grown as well as the way of life of the small farmer. These changes include the following: (1) Because better paying jobs and an enhanced lifestyle are luring farmers to the large urban areas, fewer workers are available for labor on the farms. (2) Large government subsidies have created a situation where the small farmer finds it no longer profitable to grow cereal crops as he traditionally did. (3) A lack of adequate refrigerated trucks and an increase in salinity in groundwater has caused farmers near the market centers of Makkah and Jeddah to cut fruit trees and replant with vegetables that can withstand more saline water and can be transported to the nearby markets more easily than those framers living in the farther areas of the region. What the author concludes is that increased attention to the problems of the small farmer in the region is necessary so that food supplies will be maintained to feed a growing population and so that self-sufficiency can be achieved. Additional support by the government in the way of subsidies and loans and more programs to educate farmers in marketing techniques and improved farm methods and management must be developed. And finally, the farmers should work together, sharing information and resources for the common good of all small farmers in the region.