Central Tendency and Dispersion

1
Central Tendency and Dispersion

• Univariate and Descriptive Statistics

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Frequency Table
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Central Tendency

• Mode
• Median N1
• 2
• Mean

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Valid to Use?
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Valid to Use?
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Dispersion

• Range
• Interquartile Range -

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Standard Deviation

• Average Deviation from mean?
• Intermediate points
• 1. Sum of Squares

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Standard Deviation Cont.

• 2. Variance
• Math, Not Reality

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Standard Deviation, Finally
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Distributions
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Empirical Data

• Frequency Table
• Frequency Distribution

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Normal Distribution

• Symmetrical
• Smooth
• Unimodal
• Tails never touch

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Non Normal Curves

• Skew

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• Kurtosis

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Standard Normal Distribution

• Special Version of Normal
• xbar0
• s 1

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z-scores

• How far from ybar
• Same units as s
• y observation
• ybar variable mean
• s standard deviation of the variable

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Using z-scores

• Where is the observation?
• Standardization
• Z-score chart (area under the standard normal
  curve)

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Sampling Distribution

• Sampling Error
• Central Limit Theorem
• Sampling Distribution of Means

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Standard Error

• Calculating Sample Size - (Solve for N)
• Statistical Significance