Conference on Applied Statistics in Agriculture

CONFIDENCE INTERVALS FOR SOIL PROPERTIES BASED ON DIFFERING STATISTICAL ASSUMPTIONS

Agricultural soil management is becoming increasingly precise as technology advances and as environmental concerns increase. Soil surveys are a readily available source of soils information, but soil properties are reported as generalized values or generic ranges. A need exists to define the central tendencies of soil properties in a rigorous, quantified fashion. Statistically, the central tendency is best expressed as confidence intervals about means or medians. Transect sampling was used to collect data on soil properties within a soil survey map unit. Key questions for data analysis include assumptions of independence within transects and normality. The choice of statistical method is based on assumptions about the data and on the sampling scheme. Narrower confidence intervals resulted from assumptions of independence within transects and normal distributions of soil property values. Wider confidence intervals were obtained if assumptions of independence and normality were not made. For transect sampling in general, and these data in particular, the wider confidence intervals seem most appropriate.