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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( ) Bar graphs Pie charts Graphs for quantitative variables Histograms Stemplots Stemplots versus PREP. histograms Interpreting histograms Time plots 5 Variables In a study, we collect informationdatafrom 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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 Fall '08
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