9 - Exploring a distribution: 1. Always plot your data:...

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Exploring a distribution: 1. Always plot your data: make a graph, usually a histogram or a stemplot. 2. Look for the overall pattern (shape, center, spread) and for striking deviations such as outliers. 3. Calculate a numerical summary to briefly describe center and spread. 4. Sometimes the overall pattern of a large number of observations is so regular that we can describe it by a smooth curve . Density curve: An idealized description of the overall pattern of a distribution that smooths out the irregularities in the actual data. A density curve has total area 1 underneath it. A density curve is a curve that * is always on or above the horizontal axis, and * has area exactly 1 underneath it. Outliers, which are deviations from the overall pattern, are not described by the curve. Of course, no set of real data is exactly described by a density curve. The curve is an idealized description that is easy to use and accurate enough for practical use. The median of a density curve is the equal-areas point, the point with half the area under the
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9 - Exploring a distribution: 1. Always plot your data:...

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