Medical Informatics. Учебное пособие

-a type II error (error of the second kind) is the failure to reject a false null hypothesis.

-Possible decisions, errors and their probabilities can be represented as shown in Table 2.

15. General population and sampling. Ensuring representative samples

When conducting statistical research statistical observation (examination), that is collecting complete and accurate data about the studied phenomenon, process or object, is carried out primarily.

Statistical monitoring may cover either all units without the exception that make up the studied phenomenon (or process) - in this case we speak of a continuous monitoring, or only part of them, that is, non-continuous monitoring. Statistical population, which includes all of the common units of the studied phenomenon or process, is called general population.

Continuous monitoring makes it possible to collect such data, which will provide the most complete characteristic of the phenomenon under study (the process, object), but it requires usually substantial material expenditures, engagement of a large number of workers of various qualifications, processing large volumes of collected information. A classical example of a continuous single-time statistical survey is census of population. Dispensary observation of certain categories of citizens in the regions of Russia can be attributed to continuous statistical survey, as well as collecting data on the results of annual (enhanced) medical examinations of servicemen which should be held

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with100% coverage of personnel. In the course of these surveys (raw) data are collected according to the method of continuous monitoring. The data are later on subjected to statistical analysis with calculation of statistical indicators.

It is not uncommon that in cases when the number of units of the studied phenomenon is too large or when the limited time does not allow to study all units of statistical observation, not all units, but only some of them are studied. Statistical population, which includes only part of parent population is called sampled population, or sampling.

Statistical indicators, resulting from the further data processing, as well as generalizations and conclusions obtained from sampled population, are extended with certain limitations to all studied phenomenon, that is to all parent population. This is the essence and the main advantage of discontinuous statistical monitoring method.

However, theory and practice show that generalizing statistical indicators (mean values, relative numbers), and other characteristics resulting derived from statistical processing of data based on discontinuous monitoring, as a rule, differ from related indicators calculated on the basis of a continuous monitoring, and therefore they can not be unconditionally used for objective quantitative assessment of the studies phenomenon (process) as a whole.

Package STATISTICA is a versatile integrated system that is designed for statistical analysis and data visualization, database management, and custom application development, containing a wide range of analysis procedures for use in scientific research, technology and business.

In addition to general statistical and graphical tools available in the system there are specific modules, for instance to conduct sociological or biomedical research, technical solutions, and, what is very important, industrial applications: quality control charts, processes analysis and design of experiments. Work with all modules occurs within a single software package, for which you can choose one of several proposed user interfaces.

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