Basic concept in Stat

• 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 nominal level of measurement is characterized by data that consists of names, level labels, or categories only.
• Random sampling is done by using chance or random numbers
• Systematic sampling 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