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Chapter Two

Describing, Displaying, and Exploring Statistical Data

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03/05/2003 Week #2 江支弘

Displaying Data 展示數據

First step in data analysis電子試算表與統計圖表Overall pattern 整體型態 /趨勢 v.s. Exception

sFrom graph to numerical description

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03/05/2003 Week #2 江支弘

Scatter plot

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Box plot

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Displaying Distributions 呈現分佈

Distribution of a variable: what values the variable takes and how often each value occurs

Histogram 直方圖Ex8: percent of age 65 or older, by state, p1

50中文

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03/05/2003 Week #2 江支弘

How to make a histogram 直方圖的製作

(Ex8) Step 1 數據分組 : divide the range of the data into classes of equal width

Step 2 分組統計次數 : count the # of observations in each class

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Step 3: Draw the histogram

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Interpreting histograms

與長條圖不同 : base scale; width of bar; Pattern and deviations 型態與偏差Outlier 離群值 : an individual observation that f

alls outside the overall patternOverall pattern of a distribution 分佈的一般型態

Center and Spread 中心與離度

Shape (e.g. symmetric)

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Symmetric and Skewed distributions對稱分佈與偏斜分佈

A distribution is

Symmetric if the right and left side of the histogram are approx. mirror images of each other

Skewed to the right if the right side of the histogram (upper half) extends much farther out than the left side

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03/05/2003 Week #2 江支弘

Normal distribution

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Exponential distribution

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Uniform distribution

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Skewed distribution