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**Unformatted text preview: **1 Chapter 1 The Where, Why, and How of Data Collection 2 Chapter Goals After completing this chapter, you should be able to: Describe key data collection methods Learn to think critically about information Learn to examine assumptions Know key definitions 3 Descriptive statistics Collecting, presenting, and describing data Inferential statistics Drawing conclusions and/or making decisions concerning a population based only on sample data Tools of Business Statistics 4 Descriptive Statistics Collect data e.g., Survey, Observation, Experiments Present data e.g., Charts and graphs Characterize data e.g., Sample mean = n x i ∑ Displaying distributions with graphs Variables Types of variables Graphs for categorical variables( 分分分分 ) Bar graphs Pie charts Graphs for quantitative variables Histograms 分分分分分 Stemplots 分分分分分 Stemplots versus 分 PREP. 分分 histograms Interpreting histograms 分分分分分分分分分 Time plots 5 Variables In a study, we collect information—data—from individuals . Individuals can be people, animals, plants, or any object of interest. A variable is any characteristic of an individual. A variable varies among individuals. Example: age, height, blood pressure, ethnicity, leaf length, first language The distribution （（（（ of a variable tells us what values the variable takes and how often it takes these values. 6 Two types of variables Variables can be either quantitative… Something that takes numerical values for which arithmetic operations, such as adding and averaging, make sense. Example: How tall you are, your age, your blood cholesterol level, the number of credit cards you own. … or categorical. Something that falls into one of several categories. What can be counted is the count or proportion of individuals in each category. Example: Your blood type (A, B, AB, O), your hair color, your ethnicity, whether you paid income tax last tax year or not. 7 How do you know if a variable is categorical or quantitative? Ask: What are the n individuals/units in the sample (of size “ n ”)? What is being recorded about those n individuals/units? Is that a number ( quantitative) or a statement ( categorical)? Individuals in sample DIAGNOSIS AGE AT DEATH Patient A Heart disease 56 Patient B Stroke 70 Patient C Stroke 75 Patient D Lung cancer 60 Patient E Heart disease 80 Patient F Accident 73 Patient G Diabetes 69 Quantitative Each individual is attributed a numerical value. Categorical Each individual is assigned to one of several categories....

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