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**CHAPTER 1:**INTRODUCTION**WHAT IS STATISTICS?**• Definition • Statistics is a group of methods used to collect, analyze, present, and interpret data and to make decisions.**TYPES OF STATISTICS**• Definition • Descriptive Statistics consists of methods for organizing, displaying, and describing data by using tables, graphs, and summary measures.**TYPES OF STATISTICS**• Definition • Inferential Statistics consists of methods that use sample results to help make decisions or predictions about a population.**POPULATION VERSUS SAMPLE**• Definition • A population consists of all elements – individuals, items, or objects – whose characteristics are being studied. The population that is being studied is also called the target population.**POPULATION VERSUS SAMPLE cont.**• Definition • A portion of the population selected for study is referred to as a sample.**Figure 1.1 Population and sample.**Population Sample**POPULATION VERSUS SAMPLE cont.**• Definition • A survey that includes every number of the population is called a census. The technique of collecting information from a portion of the population is called a sample survey.**POPULATION VERSUS SAMPLE cont.**• Definition • A sample that represents the characteristics of the population as closely as possible is called a representative sample.**POPULATION VERSUS SAMPLE cont.**• Definition • A sample drawn in such a way that each element of the population has a chance of being selected is called a random sample. If the chance of being selected is the same for each element of the population, it is called a simple random sample.**BASIC TERMS**Table 1.1 2001 Sales of Seven U.S. Companies Variable An observation or measurement An element or a member**BASIC TERMS cont.**• Definition • An element or member of a sample or population is a specific subject or object (for example, a person, firm, item, state, or country) about which the information is collected.**BASIC TERMS cont.**• Definition • A variable is a characteristic under study that assumes different values for different elements. In contrast to a variable, the value of a constant is fixed.**BASIC TERMS cont.**• Definition • The value of a variable for an element is called an observation or measurement.**BASIC TERMS cont.**• Definition • A data set is a collection of observations on one or more variables.**TYPES OF VARIABLES**• Quantitative Variables • Discrete Variables • Continuous Variables • Qualitative or Categorical Variables**Quantitative Variables**• Definition • A variable that can be measured numerically is called a quantitative variable. The data collected on a quantitative variable are called quantitative data.**Quantitative Variables cont.**• Definition • A variable whose values are countable is called a discrete variable. In other words, a discrete variable can assume only certain values with no intermediate values.**Quantitative Variables cont.**• Definition • A variable that can assume any numerical value over a certain interval or intervals is called a continuous variable.**Qualitative or Categorical Variables**• Definition • A variable that cannot assume a numerical value but can be classified into two or more nonnumeric categories is called a qualitative or categorical variable. The data collected on such a variable are called qualitative data.**CROSS-SECTION VERSUS TIME-SERIES DATA**• Cross-Section Data • Time-Series Data**Cross-Section Data**• Definition • Data collected on different elements at the same point in time or for the same period of time are called cross-section data.**Time-Series Data**• Definition • Data collected on the same element for the same variable at different points in time or for different periods of time are called time-series data.**Table 1.3**Price of a 30-Second TV Commercial During Super Bowl Telecast**SOURCES OF DATA**• Data may be obtained from • Internal sources • External sources • Surveys and experiments**SUMMATION NOTATION**• Example 1-1 • Annual salaries (in thousands of dollars) of four workers are 75, 42, 125, and 61. Find • ∑x • (∑x)² • ∑x²**Solution 1-1**• ∑x = x1+ x2+ x3+ x4 = 75 + 42 + 125 + 61 = 303 = $303,000 • (∑x)² = (303)² = 91,809 • ∑x² = (75)² + (42)² + (125)² + (61)² = 5625 + 1764 + 15,625 + 3721 = 26,735**Example 1-2**The following table lists four pairs of m and f values: Compute the following: • Σm • Σf² • Σmf • Σm²f**Solution 2-1**Table 1.4