normal curve

normal curve - Quantitative Methods Chapter 3: The Normal...

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  © John M. Ackroff 2008 Quantitative Methods Chapter 3:  The Normal Curve http://www.rci.rutgers.edu/~ackroff/QM January 31, 2008
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  © John M. Ackroff 2008 The Normal Curve The Normal Curve, the Bell Curve, the  Gaussian distribution Karl Friedrich Gauss – 1777 – 1855  First to explain the concept of least squares as  best estimate. Think about what we’ve done with heights and  coin tosses. Our “best” predictions might not happen, but our total  error is minimized.
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  © John M. Ackroff 2008 The Normal Curve The Normal Distribution is the most  important Theoretical Frequency  Distribution that we will cover. It’s a compromise between J-shaped and  rectangular distributions. Neither one is particularly interesting. The compromise is!!
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  © John M. Ackroff 2008 The Normal Distribution 68.26% of the scores are within one standard  deviation of the mean 95.44% of the scores are within two standard  deviations of the mean 99.74% of the scores are within three  standard deviations of the mean If we had everyone stand up, we’d have A few really, really tall people A few really, really short people
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© John M. Ackroff 2008 What is the normal curve? Think about a histogram Think about a histogram with very small interval  sizes. Very small interval sizes   very skinny bars. Connect the midpoints of the bars, and you get a normal  curve. Given that the variable you’re measuring is normally  distrubuted. We typically make this assumption. The area under the curve between two points  represents the proportion of the data points that  fall between those limits. This is the probability that a value falls between those 
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This note was uploaded on 04/05/2008 for the course PSYCH 200 taught by Professor Ackroff during the Spring '08 term at Rutgers.

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normal curve - Quantitative Methods Chapter 3: The Normal...

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