**SSC 201 and 202 Lecture Note** – **This is a complete course material for statistics: it is a useful book that gives basic insight to statistical concepts and students in higher institutions will find it useful**

SSC 201 and 202 Lecture Note – **Statistics**Â is a branch ofÂ mathematicsÂ working withÂ dataÂ collection, organization, analysis, interpretation and presentation.Â In applying statistics to a scientific, industrial, or social problem, it is conventional to begin with aÂ statistical populationÂ or aÂ statistical modelÂ to be studied. Populations can be diverse groups of people or objects such as “all people living in a country” or “every atom composing a crystal”. Statistics deals with every aspect of data, including the planning of data collection in terms of the design ofÂ surveysÂ andÂ experiments.^{[1]}Â SeeÂ glossary of probability and statistics.

When census data cannot be collected, statisticians collect data by developing specific experiment designs and survey samples. Representative sampling assures that inferences and conclusions can reasonably extend from the sample to the population as a whole. An experimental study involves taking measurements of the system under study, manipulating the system, and then taking additional measurements using the same procedure to determine if the manipulation has modified the values of the measurements. In contrast, an observational study does not involve experimental manipulation.

Two main statistical methods are used inÂ data analysis:Â descriptive statistics, which summarize data from a sample usingÂ indexessuch as theÂ meanÂ orÂ standard deviation, andÂ inferential statistics, which draw conclusions from data that are subject to random variation (e.g., observational errors, sampling variation).^{[3]}Â Descriptive statistics are most often concerned with two sets of properties of aÂ *distribution*Â (sample or population):Â *central tendency*Â (orÂ *location*) seeks to characterize the distribution’s central or typical value, whileÂ *dispersion*Â (orÂ *variability*) characterizes the extent to which members of the distribution depart from its center and each other. Inferences on mathematical statistics are made under the framework ofÂ probability theory, which deals with the analysis of random phenomena.

Source: Wikipedia