Statistics is a branch of Mathematics that uses large sets of numerical data to obtain inferences (conclusions), based on the calculation of probabilities. On the one hand, it aims at describing data, on the other hand, at inferring events or processes based on data obtained from them. It also studies and refines the methods related to the processes, both data acquisition, and description, analysis, and conclusion.

Reasons to study Statistics:

1. It allows us to read and present research information in a standard format understandable all around the world.

2. It makes us able to understand what the data tell us and thus, be able to make better decisions (predict before something happens).

It should be clear that statistics is much more than just the tabulation of numbers and the graphical presentation of these tabulated numbers. Statistics is the science of gaining information from numerical and categorical1 data. Statistical methods can be used to find answers to the questions like • What kind and how much data need to be collected? • How should we organize and summarize the data? • How can we analyze the data and draw conclusions from it? • How can we assess the strength of the conclusions and evaluate their uncertainty?

Basic concepts:

Population and sample are two basic concepts of statistics. Population can be characterized as the set of individual persons or objects in which an investigator is primarily interested during his or her research problem. Sometimes wanted measurements for all individuals in the population are obtained, but often only a set of individuals of that population are observed; such a set of individuals constitutes a sample. This gives us the following definitions of population and sample.

Definition 1: Population is the collection of all individuals or items under consideration in a statistical study (Weiss, 1999).

Definition 2: Sample is that part of the population from which information is collected (Weiss, 1999).