Chapter-1-10-11

Chapter-1-10-11 - Chapter 1 Exploring Data Intro:...

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Chapter 1 Exploring Data
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Intro: Statistics is the science of data. We begin our study of statistics by mastering the art of examining data. Any set of data contains information about some group of individuals. The information is organized in variables. 2
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Individuals – are the objects described by a set of data. Individuals may be people, but they may also be other things. A variable – is any characteristic of an individual. A variable can take different values for different individuals. 3
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Who, What, Why When you come across a new set of data, you need to ask yourself the following questions. 1.Who? – What individuals do the data describe? How many individuals appear in the data? 2.What? – How many variables are there? What are the exact definitions of these variables? In what units is each variable recorded? 4
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Who, What, Why 3. Why? – What is the reason the data were gathered? What conclusions are we looking for? 5
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Variable Types A categorical variable – places an individual into one of several groups of categories. A quantitative variable – takes numerical values for which arithmetic operations such as adding and averaging make sense. 6
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A variable generally takes values that vary. The pattern of variation of a variable is its distribution. The distribution of a variable tells us what values the variable takes and how often it takes these values. In order to analyze data we begin by examining each variable by itself. Then move on to study relationships among the variables. Start with graphs of the distributions then add numerical summaries of specific aspects of the data. 7
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8 1.1
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A. The individuals are the BMW 318I, the Buick Century, and the Chevrolet Blazer. B. The variables given are Vehicle type (categorical) Transmission type (categorical) Number of cylinders (quantitative) City MPG (quantitative) Highway MPG (quantitative) 9 1.1 Answer
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1.3 You want to compare the “size” of several statistics textbooks. Describe three possible numerical variables that describe the “size” of a book. In what units would you measure each variable? 10 How many pages. (Number of pages) Weight (lbs) Thickness (inches)
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Displaying Distributions with graphs. There are several graphs to choose from when displaying data: bar graphs, pie charts, dot plots, stem plots, histograms, and time plots, just to name some that we will be using in this section. The purpose of a graph is to help us understand the data. It lets you look for an overall pattern and for striking deviations from that pattern. To describe the overall pattern of a distribution you start with the three biggest descriptors: shape, center, and spread. Next you can look for outliers and clusters. 11
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This note was uploaded on 12/09/2011 for the course STATS 221 taught by Professor Nielson during the Fall '10 term at BYU.

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Chapter-1-10-11 - Chapter 1 Exploring Data Intro:...

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