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# power point ch1 - Economics 41 Statistics for Economists...

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Economics 41 Statistics for Economists Professor: Bruce Brown Office Hours Wed (& every other Mon) 11:00-1:00 In Bunche 2255 [email protected]

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Text: Introduction to the Practice of Statistics by Moore, McCabe and Craig, 2009 W. H. Freeman & Co Publisher Useful, Free, Text website: http://bcs.whfreeman.com/ips6e/ Chapter quizzes will be useful, but will not directly affect grade We will follow the text closely
Chapter 1 1.1) Displaying Distributions with Graphs 1.2) Describing Distributions with Numbers 1.3) Density Curves and Normal Distribution

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Looking at Data - Distributions Displaying Distributions with Graphs IPS Chapter 1.1 © 2009 W.H. Freeman and Company
Objectives (IPS Chapter 1.1) Displaying distributions with graphs Variables Types of variables Graphs for categorical variables Bar graphs Pie charts Graphs for quantitative variables Histograms Stemplots Stemplots versus histograms Interpreting histograms Time plots

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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.
observations  = “individuals”  may be: people, states, countries, years,  companies, medicines, etc….     variables  will take on different values for  different individuals.  For example: gender,  average income, size…

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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.
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.

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power point ch1 - Economics 41 Statistics for Economists...

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