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Definition
| a measure of central tendency in a data set that is computed by adding together all te individual observations and dividing the sum so obtained by the number of observations; as a result, the sum of deviations of all observations from this mean equal zero |
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| bimodal frequency distribution |
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Definition
| a frequency distribution in which two different values occur with the highest frequency or almost that |
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| regardless of the shape of a population's frequency distribution, the proportion of observations falling wihtin k standard deviations of the mean is at least 1-(1/k^2), give that k equal 1 or more |
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| a measure of shape that classifies frequency curves as platykurtic,mesokurtic, or leptokurtic |
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| a measure of relative dispersion, equal to the ratio of the standard deviation to the arithmetic mean |
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| graphical devices that highlight the average performance of data series and the dispersion around this average so the average and dispersion of the past become standards for controlling performance in the present |
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| values in a data set that divide the array of all observations into ten parts, each of which contains0.10 (or 10 percent) of the observed values |
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| whenever a statistical population can be described, at least roughly, by the perfectly symmetrical , bell-shaped normal curve, we can estimate the percentages of all population values that lie within specified numbers of standard deviations from the mean: approximately 68 percent of all values lie within 1 standard deviation from the mean about 95 percent lie within 2 standard deviations from the mean; and practically all values lie within 3 standard deviations from the mean |
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Definition
| the 0.25 fractile (or 25th percentile) in a data set, such that a quarter (or 25 percent) of all values are smaller than or at most equal to it |
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| any value in a data set such that a specified proportion of all values is smaller than or at most equal to it |
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Definition
| distance measures of dispersion, equal to differences between two fractiles in a data set |
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| interquartile range or H-shaped |
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Definition
| a distance measure of dispersion; the difference between the third and first quartiles, containing the middle 50 percent of all values observed |
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Definition
| a measure of shape, noting a frequency curve's degree of peakedness |
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Definition
| an average measure of dispersion in a data set; it equals the arithmetic mean of all the absolute differences between each individual observation and the data set's mean (or, sometimes, median) |
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| measures of central tendency or measures of location |
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Definition
| values which observations tend to cluster and that describe the location of what in some sense might be called the "center" of a data set |
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| measures of dispersion or measures of variability |
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Definition
| numbers that indicate the spread or scatter of observations; they show the extent to which individual values in a data set differ from one another and, hence, differ from their central location |
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| numbers that indicate either the degree of asymmetry or the degree of peakedness in a frequency distribution |
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Definition
| a measure of central tendency that divides and ordered array of data into two halves; if the data are arranged in ascending order from smallest ot largest, all the observations below the median are smaller than or equal to it, while all the observations above the median are equal to it or larger. If the total number of observations is odd, the media is the middle observation in the ordered array; if the total number of observations is even, the median is the average of the two middle values |
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Definition
| the class among grouped data that contains the median |
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| the sum of data set's minimum plus maximum values, divided by 2 |
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| the class among grouped data that contains the mode |
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| a measure of central tendency that is the most frequently occurring value in a data set |
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| multimodal frequency distribution |
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Definition
| a frequency distribution in which two or more different values occur with the highest frequency or almost that |
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Definition
| a frequency curve that has the characteristics (1-3) of the normal frequency distribution |
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Term
| normal frequency distribution |
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Definition
| a population whose relative frequency density is characterized by three features (1) it is single-peaked above the population's mean,median,and mode, which coincide, (2) it is perfectly symmetric about this central value, and (3) it has tails extending indefinitely in both directions from the center, approaching, but never touch, the horizontal axis |
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Definition
| a summary measure based on population data |
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| Pearson's coefficient of skewness |
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Definition
| a measure of shape that focuses on the difference between mode and the mean and then realtes it to the standard deviation |
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Definition
| any value in data set such that a specified percentage of all values is smaller than or at most equal to it |
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| a number that describes the frequency of observations in a particular category as a fraction of all observations made |
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| values in a data set that divide the array of all observations into four quarters, each of which contains 0.25 (or 25 percent) of the observed values |
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| a distance measure of dispersion; the difference between the largest and smallest observation in a set of ungrouped data or between the upper limit of the largest class and the lower limit f the smallest class for grouped data |
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| the 0.50 fractile (or 50th percentile) in a data set, such that half (or 50 percent) of all values are smaller than or at most equal to it |
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| a measure of shape,noting a frequency distribution's degree of distortion from horizontal symmetry |
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| an average deviation measure of dispersion in a data set; equal to the positive square root of the variance |
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| a summary measure based on sample data |
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| the .75 fractile (or 75th percentile) in a data set, such that three quarters (or 75 percent) of all alues are smaller than or at most equal to it |
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Definition
| the arithmetic mean of a data set after an equal percentage of smallest and largest observations have been deleted from its ordered array |
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Definition
| an average deviation measure of dispersion in a data set; for population, it is constructed by taking the difference between each observed value and the population mean, squaring each of these deviations, and then finding the arithmetic mean of the squared values; for a sample, a roughly analogous expression is constructed with the help of the sample mean |
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Definition
| a measure of central tendency that gives unequal weights to different observations according to their unequal relative importance this special type of arithmetic mean equals the sum of the products of observed values and their respectie weight, divided by the sum of the weights |
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