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Statistics Chapter 6
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13
Mathematics
09/12/2009

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Term
Standardizing
Definition
elimination of units, standardized values can be compared and combined even if the original variables had different units and magnitudes
Term
standardized value
Definition
a value found by subtracting the mean and dividing by the standard deviation
Term
Shifting
Definition
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
Term
Rescaling
Definition
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
Term
Normal model
Definition
a useful family of models for unimodal, symmetric distribution
Term
Parameter
Definition
a numerically valued attribute of a moel, for example, the values of µ and sigma in a N model are parameters
Term
Statistic
Definition
a value calculated from data to summarize aspects of the data; for example, the mean and standard deviation
Term
z-score
Definition
a z-score tells how many standard deviations a value is from the mean; z-scores have a mean of 0 and a standard deviation of 1
Term
Standard Normal model
Definition
a Normal model, N with mean µ = 0 and standard deviation = 1, also called standard Normal distribution
Term
Nearly Normal Condition
Definition
a distribution is nearly Normal if it is unimodal and symmetric
Term
68-95-99.7 Rule
Definition
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
Term
Normal percentile
Definition
the Normal percentile corresponding to a z-score gives the percentage of values in a standard Normal distribution found at that z-score or below
Term
Normal probability plot
Definition
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