In a research study, the objects whose characteristics are studied are called units or individuals. Thus, associated with any research study, we have a set of units. The totality of (collection of all) units under consideration is called population or universe. For examples, in the study of financial condition of families of a particular tribe, the set of all families belonging to the tribe is the population. The families are the units. In the study of financial condition of families in USA, the set of all families in USA is the population. A population may be that of people, trees, fields, heights etc. A population which contains finite number of units is a finite population. A population which contains infinite number of units is an infinite population. For instance, population of students belonging to a college is finite, whereas, population of heights of plants is infinite. The units (number of population) have some characteristics. These characteristics may be numerically measurable or may not be numerically measurable. A characteristic which is numerically measurable is a quantitative characteristic and a characteristic which is not numerically measurable is a qualitative characteristic. In a population some characteristics remain the same for all units and some others vary from unit to unit. A quantitative characteristic which varies from unit to unit is an attribute. For example, height, weight etc. are variables and sex, skin color etc. are attributes. A variable may be discrete or continuous. A variable which assumes only some specified values in a given range is discrete variable. A variable which assumes all the values in the range is a continuous variable. A statistician is concerned with the study of variables which show statistical (stochastic non mathematical) variation. Such a study is called statistical investigation.
The person who conducts the statistical survey is called investigator. The investigator plans the survey, collects the required data, analyzes them and finally draw conclusion. The investigator collects information about the units of the population either directly from them or through others. The persons who supply information are informants or respondents. The investigator may directly collect information from the informants or he may collect them through his agents. These agents who collect and hand over information to the investigator are enumerators.
For a research survey of a population the investigator may collect information from each and every units belonging to the population or he may collect information from some selected representative units only. In the latter case, the group of representative units from whom information are collected is called sample. Thus sample is a representative portion of the population. A research study in which sample is made use of is sample survey and a survey in which the whole population is made use of is census enumeration. The number of units in a sample is the sample size.
The sample is then analyzed and a conclusion is made thereof.
Be the first to leave a review.