A subset of population is usually chosen in such way that it can be taken to represent the population with respect to some characteristic. (example: height, or cost, or gender, or make of car)
A list of members of the population of interest is called the sampling frame .
If each members of the sample is selected by the equivalent of drawing lots, the sample is a simple random sample or commonly a random sample.
What is Data Set?
In statistics data sets usually come from actual observations obtained by sampling a statistical population , and each row corresponds to the observations on one element of that population.
Data sets may further be generated by algorithms for the purpose of testing certain kinds of software .
What Is Variables?
The characteristic measured or observed when an experiment is carried out or an observation is made. Variables may be non-numerical or numerical. Since a non-numerical observation can always be coded numerically, a variable is usually taken to be numerical. Statistic is concerned with random variables and with variables whose measurement may involve random errors.
What Is Observation?
A result of an experiment or trial in which a variable, either numerical or categorical, is measured
What is Population?
The complete set of all people in a country, or a town, or any region.
By extension the term is used for the complete set of objects of interest.
- All cars built by a particular company in the year 2001.
- All apple sold as grade I by a particular supermarket.
These all the real population and they are finite.
It can be in the larger number.
It is also used for infinite population of all possible result of a sequence of statistic trials.