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elimination of units, standardized values can be compared and combined even if the original variables had different units and magnitudes 


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a value found by subtracting the mean and dividing by the standard deviation 


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adding a constant to each data value adds the same constant to the mean, the median, and the quartiles, but does not change the standard deviation or IQR 


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Multiplying each data value by a constant multiplies both the measures of position (mean, median and quartiles) and the measures of spread (standard deviation and IQR) by that constant 


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a useful family of models for unimodal, symmetric distribution 


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a numerically valued attribute of a moel, for example, the values of µ and sigma in a N model are parameters 


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a value calculated from data to summarize aspects of the data; for example, the mean and standard deviation 


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a zscore tells how many standard deviations a value is from the mean; zscores have a mean of 0 and a standard deviation of 1 


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a Normal model, N with mean µ = 0 and standard deviation = 1, also called standard Normal distribution 


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a distribution is nearly Normal if it is unimodal and symmetric 


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in a Normal model, about 68% of values fall within one standard deviation of the mean, about 95% fall within two standard deviations of the mean, and about 99.7% fall within three standard deviations of the mean 


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the Normal percentile corresponding to a zscore gives the percentage of values in a standard Normal distribution found at that zscore or below 


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a display to help assess whether a distribution of data is approximately Normal, if it is near straight, the data satisfy the Nearly Normal Condition 

