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Simple Quantitative Displays

Key Questions

  • A normal distribution is completely symmetrical, a skew distribution is not.

    In a positively skewed distribution, the "toe" at the larger side is longer than at the other side, causing the median, and especially the mean, to move to the right. In a negatively skewed distribution these move to the left, because of a longer "toe" at the smaller values.

    While in a non-skewed normal distribution mode, median and mean are all at the same value.

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    (pictures from internet)

  • Dotplots and stemplots are suitable for the visual representation of numerical ( quantitative) data, in particular for small to medium-sized data sets .

    For categorical (qualitative) data, the bar chart is the preferable way of visual representation.