# Statistics

Statistics can be defined as the science which deals with the collection, presentation, analysis and interpretation of data which is usually numerical. Statistics is an indispensable science that is used in all fields of human knowledge and chiefly in economics, planning, mathematics, medicine, astronomy, biology and psychology.

Descriptive statistics refers to statistical methods used for the summarization of data. This branch deals with measures of central tendency, measures of dispersion, coefficients of skewness and kurtosis and other techniques which summarize or 'describe' the observations under study.

Statistical inference deals with the drawing of inferences or conclusions about a parent population using data from a random sample. Statistical inference includes the theory of estimation and testing of hypotheses using parametric and non-parametric methods.

Mathematical statistics deals with the proving of statistical theories using known mathematical laws. The theory of probability and distribution theory are part of this field.

The word statistics can also be used to refer to numerical statements of facts, or the plural form of the word ‘statistic’ which refers to a function of sample observations.

## History

In the beginning, statistics was originally considered as the study of data. It was probably derived from German ‘statistik’ or Latin ‘status’, each of which means ‘state’.

The use of statistics can be traced to ancient times when governments began collecting data relating to the population and wealth of their countries. Examples include the ancient empires of Egypt, Persia and China which existed hundreds of years before Christ. The most impressive was that of the Roman Empire which accurately documented data about the population, area and wealth of its territories.

More systematic and advanced studies began during the Middle Ages when scientists recognized the need to summarize and analyze data. During this period, several disciplines of statistics began to appear, including mathematical statistics (which includes probability theory) and vital statistics.

Modern developments include the study of application of the subject in fields as diverse as biometry, education, genetics, agriculture, psychology and so on. The use of statistics in these fields occurs mainly due to the need of making accurate predictions from sample data for which the theory of probability plays an important role.

Some of the major contributors to the field of statistics are listed below:

• John Grant (1620 - 1674)
• Blaise Pascal (1623 - 1662)
• Pierre Fermat (1601 - 1665)
• James Bernoulli (1654 - 1705)
• De-Moivre (1667 - 1754)
• Laplace (1749 - 1827)
• Gauss (1777 - 1855)
• Francis Galton (1822 - 1921)
• Karl Pearson (1857 - 1936)
• Ronald Fisher (1890 - 1962)

## Applications of statistics

The usefulness of statistics has led to its being used in a variety of social and physical sciences, sometimes leading to the development of separate disciplines. Some of these disciplines are:

• Econometrics (the application of statistics in economics)
• Statistical quality control (used in industries for controlling production processes)
• Mathematical statistics (the application of mathematical laws for the development of statistical theories)
• Biometry (the application of statistics in biology)
• Medical statistics
• Psychometrics (the application of statistics in psychology and education)

## Statistical techniques

There are many statistical methods and techniques; the most important are listed below:

• Presentation of data, including tabulation, graphical representations (histograms, stem and leaf diagrams, etc)
• Frequency distributions
• Measures of central tendency
• Measures of dispersion
• Correlation
• Testing of hypotheses
• Analysis of variance
• Design of experiments