# Chapter 13 - Chapter 13 Notes(Student Normal Distribution...

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Chapter 13 Notes (Student) 1 Normal Distribution Strategy for Exploring Data for One Quantitative Variable: Always plot the data: Histogram or stemplot Look for the overall pattern and for striking deviations such as outliers. Describe the center and the spread with the median and quartiles or the mean and the standard deviation. New Step Sometimes the overall pattern of a large number of observations is so regular that we can describe it by a smooth curve. Density Curves Density Curve – a curve that is superimposed on a relative frequency histogram to outline the shape. The area under the density curve is 1. Easy and quick way of describing the shape of a distribution. Density Curve
Chapter 13 Notes (Student) 2 Using a Density Curve Histograms show the frequency or relative frequency of observations in each class interval. Density curves show the proportion of observations in any region by areas under the curve. Example: We have a data set of 1000 sample proportions. What proportion of the observations are greater than 0.61? Using a Density Curve Center and Spread of a Density Curve • Median – the point that divides the area under the curve in half.
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