Chapter 1 The nature of Probability and Statistics

Basics of Statistics: 1. Statistics: It is the science of conducting studies to collect, organize, summarize, analyze and draw conclusions from data. In another words, it is a scientific field of study that provides approaches to making inferences about populations based on the examinations of smaller sets of data. a. Descriptive statistics: It consists of the collection, organization, summarization and presentation of data. Examples: sample mean, median, range, standard deviation, charts, graphs, tables, etc. b. Inferential statistics: It consists of generalizing from samples to population, performing estimations and hypothesis tests, determining relationships among variables, and making predictions. Examples: Analysis of variance, test of goodness of fit, etc. 2. Goals of Statistics: To study the population To study the variation To present the data in reduced form To apply Statistics as a research tool 3. Variable: It is the representation of some characteristic of an individual that can be measured or recorded and generally can take multiple values. Examples: height, weight, etc of people. Variables whose values are determined by chance are called random variables. a. Qualitative variables (categorical variables): They are the variables which can be places into distinct categories according to some characteristics or attribute. Examples: Gender (male or female), religious affiliation (protestant, catholic, Jewish, Muslim, Buddhists, Hindus, Other, None), favorite type of music (Classical, Country, folk, Jazz, rock, etc), etc. b. Quantitative variables: They are numerical variables and can be ordered or rank. It can be further classified into two categories: i. Discrete variables: They assume values that can be counted. It has possible values from a set of separate numbers. Examples: number of children in a family, number of car accidents in Greeley, CO in December, 2010, etc.

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