16.normalandsampling.2008stud

# 16.normalandsampling.2008stud - Psyc 305 Week 9 Normal...

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Psyc 305 Week 9 Normal Distribution & Sampling

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Goals for Today’s Class At the end of the class you should: Know the properties of the normal curve. *** Be able to use the normal curve to compute the percentages and number of scores below, above, and between other scores . Understand the difference between sample and populations. Understand the basics for the the next chapter on Hypothesis Testing.
Last Class and This One 2. Inferential statistics – help us interpret the data and make inferences about the populations represented by the data Some key ingredients for inferential statistics: Probability Normal Curve Sampling

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Lessons Learned from the Dice
One Die at a Time One Die at at Time (small) One Die at at Time (med) One Die at at Time (large) 1 3 1 7 1 21 2 6 2 5 2 17 3 4 3 6 3 23 4 2 4 7 4 20 5 4 5 10 5 18 6 1 6 7 6 23 total 20 total 42 total 122 mean 3.05 mean 3.69 mean 3.54 variance 2.25 variance 2.93 variance 2.99 st dev 1.50 st dev 1.71 st dev 1.73 DICE DEMONSTRATION 0 1 2 3 4 5 6 7 1 2 3 4 5 6 0 2 1 0 2 4 6 8 10 12 1 2 3 4 5 6 0 2 1 0 5 10 15 20 25 1 2 3 4 5 6

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Lessons Learned from the Dice 0 5 10 15 20 25 30 56 58.5 61 63.5 66 68.5 71 73.5 76 78.5 81 height-ratio Histogram But -- it’s not just for the dice. ..
Several Dice at a Time Dice Throwing Demonstration of Distributions One Die at at Time Two Dice -- Average Five Dice -- Average 1 21 less or = 2 17 less or = 2 2 2 17 over 2 to = 3 24 over 2 to = 3 33 3 23 over 3 to = 4 45 over 3 to = 4 55 4 20 over 4 to = 5 22 over 4 to = 5 27 5 18 over 5 to = 6 14 over 5 to = 6 5 6 23 total 122 122 122 mean 3.54 3.43 3.50 variance 2.99 1.39 0.72 st dev 1.73 1.18 0.85 0 5 10 15 20 25 1 2 3 4 5 6 0 10 20 30 40 50 less or = 2 over 2 to = 3 over 3 to = 4 over 4 to = 5 over 5 to = 6 0 10 20 30 40 50 60 less or = 2 over 2 to = 3 over 3 to = 4 over 4 to = 5 over 5 to = 6

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Normal Distribution Symmetric Mean = Median = Mode Another property of the normal curve -- specific variability Mark the standard deviations 68% of scores are within 1 SD of mean 95% of scores are within 2 SD of mean 99% of scores are within 3 SD of mean
E.g., Short Term Memory = 7 +/- 2

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## This note was uploaded on 09/25/2008 for the course PSYCH 305 taught by Professor Freeman during the Fall '08 term at UVA.

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16.normalandsampling.2008stud - Psyc 305 Week 9 Normal...

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