STA 301 Important definition part-1

 INTRODUCTION TO THE STATISTICS

History of the statistics:

                        Statistics is a very old word. It is from the English language. The word Statistics comes from three different languages,

                                                Latin Word                 Status

                                                Italian Word                Statista

                                                German Word             Statistik

All these words mean “The political state”. In early ages the word statistics means “The information useful to the state”.

Observation:

                        In Statistics observations are the recordings of information in numerical form. For example height of students, height of plants, weight of students etc

Data:

                        Collection of facts and figures is called data.

Population or Statistical Population:

                        Population is defined as “ The collection of all individuals which posses some common characteristics. For example height of students, Number of children, Number of fans, etc. The size of population is denoted by “ N ”.

Sample:

                        Any part of the population is called sample. On the basis of sample study we draw conclusions about the population. The size of sample is denoted by “ n ”.

Parameter:

                        Any quantity computed from the population is called parameter. Parameters are constants and usually unknown. For example populations mean µ, population variance σ²

 are the parameters.

Statistic:

                        Any quantity computed from the sample is called statistic. Statistic is variable because it varies from sample to sample. For example sample mean , sample variance S².

Branches of Statistics:

                        Statistics may be divided into to two branches:

1.                  Descriptive Statistics

2.            Inferential Statistics 

STA 301 Important definition part-2

Descriptive Statistics:

                        It is the branch of statistics which deals with the methods and principles of data collection and their presentation in meaningful form.

Inferential Statistics:

It is the branch of statistics which deals with the methods and procedures of drawing conclusion about the population on the basis of information obtained from the sample.

Variable:

                        Any characteristic that varies from one individual or an object to another.

Or

                       Any quantity that can be changed is called variable. For example age, height of students, number of children. A variable is denoted by x, y or z etc.

Constant:

                       Any quantity that can not be changed is called constant. For example 5, 12, ℮, п, etc.

Quantitative Variable:

                        If a variable can assume a numerical value is called quantitative variable. For example height, weight, number of students, etc. Quantitative variable is also called attribute of categorical variable.

Qualitative Variable:

                        If a variable can not assume a numerical value is called qualitative variable. For example eye colour, body colour, sex, intelligence, honesty, etc.

Types of Quantitative variable:

                                      It has two main types:

1.                              Discrete Variable

2.                              Continuous Variable

Discrete Variable:

                        A variable is called discrete if it can take values in whole numbers. A discrete variable represents countable data. For example number of children in a family, number of fans, etc.

Continuous Variable:

                        A variable is called continuous if it can take all possible values within an interval. A continuous variable represents measurable data. For example height and weight of students, temperature, etc.