# Statistics Ch 3

 The flashcards below were created by user firefly501 on FreezingBlue Flashcards. Density Curve Mathematical model of a distributionTotal area under the curve is equal to 1, or 100%Normal distributions: symmetrical, bell- shaped density curves defined by a mean and astandard deviation. Emprirical Rule About 68% of all observations are within 1 standard deviationof the mean.About 95% of all observations are within 2 standard deviations of the mean.Almost all (99.7%) observations are within 3 standard deviations of the mean. z-score Standardize our data to transform any Normal curve N (μ, σ) into the standard Normalcurve N (0,1).A z-score measures the number of standard deviations that a data value x is from themean μ z = (x -µ) / σ When x is larger than the mean, z is positive.When x is smaller than the mean, z is negative. Standard Normal Probabilities Table A gives the area under the standard Normal curve to the left of any z-value.When you know the proportion, but you don’t know the x-value that represents the cutoff,you need to use Table A backward. Authorfirefly501 ID137592 Card SetStatistics Ch 3 DescriptionThe Normal Distributions Density curves, z- score, standard Normal probabilities (Table A) Updated2012-02-25T16:49:52Z Show Answers