Basic Types of Sampling

In general, three broad methods are available for planning a sampling procedure [GARFIELD, 1989] probability sampling, nonprobability sampling, and bulk sampling. 

The theoretical fundamentals of these methods are described by KRISHNAIAH and RAO [1988]. These basic types can be realized as  

The main problem of random sampling is that the experience of the person who is sampling is very important and can strongly influence any systematic investigation or input hypothesis [NOTHBAUM et al., 1994], The most important subjective distortions may be  

Simple random sampling should, therefore, generally be used either in conjunction with other sampling methods or in cases involving only small study populations [SPRINGER and McCLURE, 1988], 

Important empirical criteria for finding homogeneous subareas may be [WEHRENS et al., 1993]  

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Three basic types of sampling programs are typically executed during a PCDD decontamination effort, in the following sequence ... 

The two basic types of sample holders, the block and isolated-container types, are compared in Table 5.3 (84). 

Random sampling is the most basic type of sampling and only represents the composition of the bulk material at the time and place it was sampled. 

Table 1 lists some of the materials typically analyzed by SSMS and some of the forms in which these materials may exist. The basic requirement is that two conducting electrodes be formed of the material to be analyzed. Details of the analysis of each type of sample will be discussed in a later section. 

IWo basic types of questionnaires can be used yes/no or open-ended. A sample yes/no questionnaire is provided in Figure 4-6 Figure 4-7 displays an open-ended version. The yes/no questionnaire confirms the existence of specific PSM program components or management system characteristics, while an open-ended questionnaire requires an explanation of the response and can be used to invite discussion. Yes/no questionnaires can be filled out by the facility or can be administered by less experienced assessors. Open-ended questionnaires require more experienced assessors, who are equipped to guide discussion and probe for further information. 

Spectrophotometry. The instrument generally used for this basic type of measurement is the spectrophotometer. The data obtained, usually pictured in the form of a spectrophotometric curve, indicate the ability of the sample to transmit or reflect light of the various wave lengths. Various instruments are available which can be used to determine more or less complete spectrophotometric curves. 

All these results have confirmed that the described methodology can be used for the identification of proteinaceous binders in solid samples taken from historical objects. The method facilitates the distinction of the basic types of proteinaceous additives (milk proteins from collagenous, etc.) that are contained in low concentrations in medieval or even older samples. 

For the purpose of sample introduction, any sample introduction system (also sample inlet system or inlet) suitable for the respective compound can be employed. Hence, direct probes, reservoir inlets, gas chromatographs and even liquid chromatographs can be attached to an El ion source. Which of these inlet systems is to be preferred depends on the type of sample going to be analyzed. Whatever type the inlet system may be, it has to manage the same basic task, i.e., the transfer of the analyte from atmospheric conditions into the high vacuum of the El ion source Table 5.1 provides an overview. 

It appears in this formula thati is only a function of absolute temperature. In practice, no glass electrode has this theoretical response in all types of samples and over the whole pan scale. Nevertheless, if either too acidic or too basic pan values are excluded, it is generally found that the departure from ideal behavior can be neglected. 

Together with the other chemicals-related projects in the [riw] program (INNOCHEM and COIN) an abstract model of the innovation system was drawn up according to Hemmelskamp 2000 . To obtain a more generalisable understanding of chemicals-related innovation systems, the results of the case samples and the hypothesis development were also interlinked and abstracted in such a way that two basic types of innovation systems were able to be identified and illustrated towards the end of the project. 

Three basic types of catalysts were studied in these experiments Pt-10% Rh gauzes, foam monoliths, and extruded monoliths. The gauze catalysts were 40 mesh (40 wires per inch) or 80 mesh R-10% Rh woven wire samples which were cut into 18 mm diameter circles and stacked together to form a single gauze pack 1 to 10 layers thick. Gauze catalysts are used industrially in the oxidation of hftls to NO for HNO3 production and in the synthesis of HCN from NH3, CH4, and air. 

Most of the analytical techniques applied in art conservation research require the preparation of the sample prior to the analysis step. Although the sample preparation procedures vary in a wide range, five basic types of procedures can be established grinding, dissolving, derivatizing, melting and embedding. 

There are two basic types of detectors used to measure ion signals, current detectors and ion counters. Each type has different implementations. A third type of detector is an imaging detector. In some SIMS instruments, the mass spectrometer is also an ion microscope, which transmits a stigmatic image of the sample to a detector plane. 

Procedures for isolation and measurement of lipids in foods include exhaustive Soxhlet extraction with hexane or petroleum ether (AOAC, 1995 see Basic Protocol 1), chloro-form/methanol (Hanson and Olley, 1963 Ambrose, 1969), chloroform/methanol/water (Folch et al., 1957 Bligh and Dyer, 1959 see Basic Protocol 2 and Alternate Protocol 2), acid digestion followed by extraction (see Basic Protocol 4), or, for starchy material, extraction with n-propanol-water (e.g., Vasanthan and Hoover, 1992 see Basic Protocol 3). Each method has its own advantages and disadvantages and successful measurement of lipid content is often dictated by the type of sample and extraction medium employed. Commercial extraction and preparation of edible oils are explained in the literature (Williams, 1997). 

The two basic types of water sample are discrete samples and composite samples in the majority of cases, each type supplies slightly different information on the water body in question. They are depicted graphically in Figure 1.1. 

Two basic types of flame atomising systems have been used for atomic absorption. Firstly, the total consumption or turbulent burner system in which the total sample aerosol in the oxidant stream and the fuel gas are fed separately through concentric tubes to the burner jet, where the flame is burned. Considerable turbulence, both optical and acoustic, takes place. On the positive side these burner systems are very simple in construction and thus were cheap to manufacture, did not flash-back and could handle virtually any mixture of gases. However, this system is now obsolete. 

There are two basic types of transient dynamic mechanical experiments which were performed In this study. The first type Involves Isothermal cycling of an epoxy sample between a dry and wet environment. The second type of experiment Involves cycling the epoxy sample between two different temperatures under a liquid water environment. In each case, the transient and equilibrium values of dynamic mechanical properties change In a unique manner. 

If the pressure is released from a sample of reservoir crude oil the quantity of gas evolved depends upon the conditions of liberation. There are two basic types of gas liberation fiash and differential. In a fiash liberation the pressure is reduced by a finite amount and after equilibrium is established the gas is bled off, keeping the pressure constant. In a differential liberation the gas evolved is removed con-... 

Once the sample reaches the chromatographic column, the separation process starts. The time necessary for a component injected into the chromatographic column to elute is called the absoiute retention time tR. The separation is based on different retention times of the components of the mixture. These retention times are different because the partition of each analyte between the two phases, the gas phase in motion and the stationary phase, are different. Hydrogen, helium, and nitrogen are common gases used as mobile phase. Two basic types of columns are known packed columns containing solid support particles coated with the stationary phase, and open-tubular columns with the stationary phase as a film on the inner wall (capillary columns). Because the retention time tpfi) of the analyte i is temperature dependent, the chromatographic column of any (GC) is put in an oven with temperature control capability. 

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