STATISTICS FOR ENVIROMENTAL STUDIES FARIKHIN DEPARTEMEN MATEMATIKA FAKULTAS SAINS DAN MATEMATIKA UNIVERISTAS DIPONEGORO

SUBJECTS SAMPLING and SURVEY MULTIVARIATE ANALYSIS : MULTIPLE REGRESSION, FACTORS ANALYSIS AND PCA, et. al.

PRELUDE Most scientific disciplines are concerned with measuring items and collecting data. With usage of statistics, data can be used to 1.Summarize a situation 2.Model experimental outcome 3.Make a decision

PRELUDE Statistics (tools) can be viewed as follows : Descriptive (valid if data = population) Inference (generalization) Forcasting Compare this with usage of statistics

THE DATA Data are easy to collect but difficult to interpret unless they are drawn from a well-defined population of environmental units. The definition of the population is aided by viewing the population in a space-time framework.

OBJECTIVES OF ENVIRONMENTAL POLLUTION STUDIES 1.Monitoring. Data may be collected (a) to monitor or to characterize ambient concentrations in environmental media (air, water, soil, biota) or (b) To monitor concentrations in air and water effluents.

OBJECTIVES OF ENVIRONMENTAL POLLUTION STUDIES 2.Research. Field and laboratory data may be collected (a) to study the transport of pollutants through the environment by means of food chains and aerial pathways to man and (b) to determine and quantitate the cause-and-effect relationships that control the levels and variability of pollution concentrations over time and space

FOUNDATION OF FIELD SAMPLING DESIGN 1.SAMPLING IN SPACE AND TIME Environmental sampling can be viewed in a structured way by a space-time framework. Measurements or samples (soil, water, air) may be taken at each location and point in time. Alternatively, several samples collected over time or space may be combined and mixed to form a composite sample.

FOUNDATION OF FIELD SAMPLING DESIGN 2.TARGET AND SAMPLED POPULATION The target population is the set of N population units about which inferences will be made. The sampled population is the set of population units directly available for measurement. Population units are the N objects (environmental units) that make up the target or sampled population

2.TARGET AND SAMPLED POPULATION EXAMPLES OF POPULATION UNITS : Ten-gram aliquots of soil taken from a sample of field soil that undergo specified preparatory procedures, such as drying, grinding, and so on, and that will be analyzed for pollutants according to a specified procedure Air filters exposed for a specified time interval that undergo specified procedures for chemical analysis Aboveground vegetation from 2-m x 2-m plots that is dried and ashed according to prescribed procedures in preparation for wet chemistry analysis.

2.TARGET AND SAMPLED POPULATION The concepts of target and sampled populations are illustrated in the following figure. The 14 population units in A and B make up the target population.

2.TARGET AND SAMPLED POPULATION If only the 7 units in B are available for selection and measurement, then B is the sampled population. If all 14 units are available, then the sampled population and target population are identical, the ideal situation. Statistical methods cannot be used to make inferences about A + B (the target population) if only the units in B are available for selection.

FOUNDATION OF FIELD SAMPLING DESIGN 3. REPRESENTATIVE UNITS A representative unit is one selected for measurement from the target population in such a way that it, in combination with other representative units, will give an accurate picture of the phenomenon being studied. Sometimes a list of guidelines for obtaining representative samples will be constructed.

FOUNDATION OF FIELD SAMPLING DESIGN 4. CHOOSING A SAMPLING PLAN Once the space-time framework is established and the target and sampled populations are clearly defined, a sampling plan can be chosen for selecting representative units for measurement. The choice of a plan depends on study objectives, patterns of variability in the target population, cost-effectiveness of alternative plans, types of measurements to be made, and convenience.

FOUNDATION OF FIELD SAMPLING DESIGN 5. ENVIRONMENTAL VARIABILITY Environmental variability is the variation in true pollution levels from one popUlation unit to the next. Some factors that cause this variation are Distance, direction, and elevation relative to point, area, or mobile pollution sources Non-uniform distribution of pollution in environmental media due to topography, hydrogeology, meteorology, action of tides, and biological, chemical, and physical redistribution mechanisms Diversity in species composition, sex, mobility, and preferred habitats of biota Variation in natural background levels over time and space.

FOUNDATION OF FIELD SAMPLING DESIGN 6. ERROR IN ENVIRONMENTAL STUDIES Bias, Precision, and Accuracy Random Sampling Errors