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Unformatted text preview: Click to edit Master subtitle style CHAPTER 7 Inferential Statistics: The Surprising Story of the Normal Curve The Normal Curve: It’s Everywhere! The BellShaped Curve The Normal curve is unimodal and symmetrical Three Things to Know About the 1. The approximate shape of the normal curve is everywhere (ubiquity). 2. The bell shape of the normal curve may be translated into percentages (standardization). 3. A distribution of means produces a bellshaped curve even if the original distribution of individual scores is not bellshaped, as long as the means are from sufficiently large samples (Central Limit Theorem) Figure 72: Sample of 5 Figure 73: Sample of 30 Figure 74: Sample of 140 As the sample size increases, the shape of the distribution becomes more like the normal curve. Can you think of variables that might be normally distributed? • Think about it: Can nominal (categorical) variables be normally distributed? Standardization, z Scores, and the Standardization: allows comparisons • z distribution • Comparing z scores z = (X  µ) / σ Putting z scores to work • Transforming z scores to percentiles Figure 75: The AllEncompassing z Distribution Figure 76: The Normal Curve and Percentages Check Your Learning If the mean is 10 and the standard deviation is 2 • If a student’s score is 8, what is z ?...
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This note was uploaded on 09/30/2011 for the course PSY 3301 taught by Professor Staff during the Spring '08 term at Texas State.
 Spring '08
 staff

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