POPUALTION AND SAMPLE

A population is the complete set of all items in which an investigator is interested. A population is the set of all of the outcomes from a system or process that is to be studied. N represents the population size.

Other examples of populations might be:
•    Names of all the registered voters in Bangladesh.
•    Income of all families living in Dhaka city.
•    Costs of all claims for medical insurance coverage received by a company in a given year.
•    Grade point average (GPA) of all students in NSU.

Sample:

A sample is an observed subset of population values with sample size given by n.

Random Sampling
Simple random sampling is a procedure used to select a sample of n objects from a population in such a way that each member of the population is chosen strictly by chance, each member of the population is equally likely to be chosen, and every possible sample of a given size, n, has same chance of selection.

Parameter and Statistic

A parameter is a specific characteristic of a population. A statistic is a specific characteristic of a sample.

Data:

The raw material of statistics is data. We may define data as numbers. Data are collections of any number of related observations.