IPS_chapter01.1

# IPS_chapter01.1 - Looking at data distributions Displaying...

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Looking at data: distributions Displaying distributions with graphs IPS chapter 1.1 © 2006 W.H. Freeman and Company Rev. 2006 T.F. Devlin

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Outline (Chapter 1.1) Introduction Looking at categorical variables Bar graphs Looking at quantitative variables Interpreting the graph Constructing the graph
Statistical Science Statistics is the Science of Data and Variability. What is Statistics? What is Data?

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Statistical Science Statistics is the science of data and variability. Data are not just numbers.
Statistical Science Statistics is the Science of Data and Variability. Data are numbers and values with a context . Who What Why Data are not just numbers .

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Statistical Science Statistics is the science of data. Data are not just numbers. Data are numbers and values with a context . Who, what, why Who are the objects described by the data? Individuals What are the characteristics of the individuals? Variables .
Variables In a study, we collect information—data—from individuals . Individuals can be people, animals, plants, or any object of interest. A variable is a characteristic that varies among individuals in a population or in a sample (a subset of a population). 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.

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Two types of variables Variables can be either quantitative… Something that can be counted or measured for each individual and then added, subtracted, averaged, etc. across individuals in the population. 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:

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IPS_chapter01.1 - Looking at data distributions Displaying...

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