statistics

Statistics

It is the science of conducting studies to collect, organize, summarize, analyze, and to draw conclusions from data.

Variable

A characteristic or a tribute that can assume different values

Data or Datum

A data value is the value that a variable can assume

Descriptive Statistics

The collection, organization, summarization, and presentation of the data

Population

All subjects being studied

Sample

A subgroup of an entire population

Inferential Statistics

It is the branch that deals with the generalization from a sample to a population

Qualitative Variables

Variables placed into categories based on characters like religion or gender

Quantitative Variables

Variables that are numerical and can be ordered or ranked

Continuous variables

Variables that are numerical and can be ordered or ranked such as children in a family (whole numbers only)

Measurement Scale

Describes how variables are categorized, counted, or measured

Nominal

Classes data into groups that are mutually exclusive, no order or rank is imposed.

Ex: eye color or gender

Ordinal

Classes data into groups that can be ranked but there are no precise differences between ranks. Ex: poor, good, or excellent rating of a restaurant (matter of personal opinion)

Interval

Ranks data with precise differences but there is no true zero. Ex: SAT scores, IQ scores

Ratio

Ranks data with precise differences but has a true zero. Ex: height, weight, time

Random sampling

Members of a sample are selected randomly but chance

Systematic sampling

Number each subject in a population and select every 5th or any number.

Stratified sampling

A population is divided into groups and then a sample is taken from each group. Ex: 100 people from the Freshman class, sophomore class, junior, and senior to get a sample.

Cluster sampling

A population is divided into groups called clusters by some means such as geographic area.

Convenience sampling

A very easy sample because it take from the population based on convenience.

Ex: interviewing the first 25 people to come out of a mall. (Not a good way to sample)