Statistics is a collection of methods for planning experiments, obtaining data, and then analyzing, interpreting, and drawing conclusions based on the data.
Data are the values that the variables can assume.
A variable is a characteristic that is observable or measurable in every unit of universe or population.
A population is the set of all possible values of variables.
A sample is a subgroup or the subset of a population.
Data can be classified into two types: qualitative variables, which are words or codes that represent a class or category, and quantitative variables, which are numbers that represent an amount or account.
Quantitative variables are further classified into discrete variables, which can be counted, and continuous variables, which can assume all values between any two specific values.
Data can be measured at four levels of measurement: nominal, ordinal, interval, and ratio.
The nominallevelofmeasurement is characterized by data that consists of names, level labels, or categories only.
Random sampling is done by using chance or random numbers
Systematicsampling is done by numbering each subject of a population and then selecting nth number
Stratified sampling, where population has a distinct groups, it is possible to divide the population into these groups and to draw SRS's from each of the groups
Cluster sampling uses intact group called clusters