Chapter 1


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CHAPTER 1: WHAT IS STATISTICS? 1.1 AN OVERVIEW OF STATISTICS DEFINITION 1.1: STATISTICS Statistics is the science of learning from data. This means that statistics is a method of extracting information from data. It involves rules and procedures for collecting (by statistical surveys), classifying, summarizing, presenting (in tabular or graphical form; or by summary statistics), analyzing and interpreting numerical information to assist in making prompt and more effective decisions when faced with uncertainty. The work of the statistician is no longer confined to gathering and tabulating data, but is chiefly a process of interpreting the information and making predictions. In making predictions, statistics uses the companion subject of probability . The development of the theory of probability increased the scope of statistical applications. Many data can be approximated accurately by certain probability distributions, and the results of probability distributions can be used in analyzing statistical data. Probability can be used to test the reliability of statistical inferences and to indicate the kind and amount of data required for a particular problem. Today, statistics has become an important tool in the work of many academic disciplines such as medicine , psychology , education , sociology , engineering and physics , just to name a few. Statistics is also important in many aspects of society such as business , industry and government . Because of the increasing use of statistics in so many areas of our lives, it has become very desirable to understand and practice statistical thinking. This is important even if you do not use statistical methods directly. 1.2 EXPERIMENTAL UNIT and TYPES OF VARIABLE DEFINITION 1.2: EXPERIMENTAL UNIT An experimental unit (or observational unit ) is an object or individual ( e.g. , thing, transaction, event, activity, or person, or some unified group or institution) upon which we collect data either in an experiment or in an observational study , respectively. When an experimental unit (or observational unit ) deals with human beings , experimental units (or observational units ) are called subjects or participants . Dr. LOHAKA – QBA 2302 Chapter 1: WHAT IS STATISTICS? Page 1
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DEFINITION 1.3: VARIABLE A variable is any measurable characteristic, feature, or property of an experimental unit (or observational unit) that can have different values from one time to the next or from one individual to another. We use the capital letters, such as T , X , Y , and Z , to stand for the names of variables. DEFINITION 1.4: CONSTANT We also use the lowercase letters, such as t , x , y , z, a , and others, to stand for constants . A constant is a characteristic that stays the same throughout a statistical study. In addition to using letters to represent variable names, we can employ characteristics to
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