Normal

Center and spread

Examine the distribution of a variable

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Rare and Common

How normal is normal? This app gets students to contrast their everyday notion of 'normal' to the distribution of the same name.

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Common, uncommon, and rare

Using the z-score to express everyday concepts of common and rare.

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Shapes of distributions

Introduces terms such as skew, bi-modal, and flat, by reference to the difference of the actual variable from a theoretical normal distribution.

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Parameters of the normal distribution

Normal distributions are a *family*. The specific members of the family are identified by two parameters: the mean and the standard deviation.

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Comparing two confidence intervals

Using plain confidence intervals on the mean to decide if there's good evidence that the means are different.

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