Acta medica Croatica : c̆asopis Hravatske akademije medicinskih znanosti
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Variable presents any measurable quality of an individual or a system. Data are collected by measuring variables. There are four scales of measurement: nominal, ordinal, interval and ratio. ⋯ Computer programs offer a full range of statistical procedures and calculations. In order to use them it is necessary to be familiar with some basics in biostatistics. This lecture is an introduction to the types of data, levels of measurement, ways of summarizing data and types of distributions.
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In the study of the difference between the two or more data groups, first a scientific hypothesis is to be presented involving guessing, questing, and hypothesizing that motivate research. Statistical hypothesis is drawn from the scientific hypothesis, namely, the hypothesis of the researcher (which, as a rule, is affirmative). The mode of statistical hypothesis is presented so as to be valued by statistical and analytical procedures. ⋯ The choice of the corresponding statistical test depends on the researcher's design (dependent or independent study design of two or more data samples) as well as on the nature of data (distribution normality and variance homogeneity). Parametric tests carry more strength (the power to detect the difference if in reality it really exists) than nonparametric or distribution free tests. The latter are practical for smaller samples and situations in which the conditions for conducting parametric tests have not been satisfied.