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24 Cards in this Set
- Front
- Back
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Central Tendency
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A statistical measure to determine a single sore that defines the center of a distribution. The goal of central tendency is to find the single score that is most typical or most representative of the entire group.
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Mean
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the sum of the scores divided b y the number of scores (a balance point for a distribution)
µ |
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Weighted Mean
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combined sum / combined n
or |
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Median
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the score that divides a distribution in half so that 50% of the individuals in a distribution have scores at or below the median / its purpose is to determine the midpoint of a distribution
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Mode
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In a frequency distribution, this is the score or category that has the greatest frequency.
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Central Tendency
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A statistical measure to determine a single sore that defines the center of a distribution. The goal of central tendency is to find the single score that is most typical or most representative of the entire group. Measures of central tendency include: median, mean, mode.
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Mean
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the sum of the scores divided b y the number of scores (a balance point for a distribution)
µ |
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Weighted Mean
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the average of two means, calculated so that each mean is weighted by the number of scores it represents
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Median
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the score that divides a distribution in half so that 50% of the individuals in a distribution have scores at or below the median / its purpose is to determine the midpoint of a distribution
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Mode
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In a frequency distribution, this is the score or category that has the greatest frequency.
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Why is it often viewed inappropriate to use the mean to describe central tendency for ordinal data?
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Because ordinal measurements allow you to determine direction (greater or less than) but do not allow you to determine distance. Median is compatible with this type of measure because it is defined by direction; half of the scores are above the median and half are below the median.
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Why is the Mode commonly used to describe central tendency for nominal data?
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Nominal categories are differentiated only by name, and do not measure quantity, distance or direction, hence it is impossible to compute a mean or median for data from a nominal scale.
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Perfect Symmetrical Distribution
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When the mean and median are the same
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Which measure of central tendency is most likely to be affected by one or two extreme scores in a distribution? Mean, Median or Mode?
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Mean
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variability
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a quantitative measure of the degree to which scores in a distribution are spread out or clustered together
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range
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the distance from the largest score to the smallest score in a distribution. usually defined as the difference between the upper real limit and the lower real limit of X values
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Interquartile range
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the range covered by the middle 50% of the distribution
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Semi-interquartile range
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half of the interquartile range
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deviation
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the distance from the mean
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population variance
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equals the mean squared deviation. variance is the average squared distance from the mean.
=SS/n = Σ(X-µ)² / n |
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standard deviation
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the square root of the variance
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SS (sum of square)
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the sum of the squared deviation scores
SS= Σ (X-µ)² OR SS = ΣX² - (ΣX)²/n |
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Variance formula
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SS/n
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Degrees of Freedom or df
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df=n-1
degrees of freedom determine the number of scores in the sample that are independent and free to vary |
