monday, october 1
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Monday, October 1. Distributions, Percentiles, and Central Tendency. The ogive gives you a good view of the relationship between scores and percentile rank. Household Income by Language Group (Source: 1990 Census of Population and Housing). - PowerPoint PPT PresentationTRANSCRIPT
Monday, October 1
Distributions, Percentiles, and Central Tendency
The ogive gives you a good view of the relationship between scores and percentile rank.
Household Income by Language Group (Source: 1990 Census of Population and Housing)
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Household Income
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HmongCambodianLaoSpanishSamoanArmenianTonganIndonesianVietnameseRumanianPortugueseRussianArabicKoreanPersianUkrainianChinesePunjabiJapanesePilipino IlocanoHindi
A percentile rank of a score is a single number that gives the percent of cases in the specific reference group scoring at or below that score.
A percentile rank of a score is a single number that gives the percent of cases in the specific reference group scoring at or below that score.
The mode.
The mode is the score with the highest frequency of occurrences.
It is the easiest score to spot in a distribution.
It is the only way to express the central tendency of a nominal level variable.
The median.
The median is the middle-ranked score (50th percentile).
If there is an even number of scores, it is the arithmetic average of the two middle scores.
The median is unchanged by outliers. Even if Bill Gateswere deleted from the U.S. economy, the median asset of U.S. citizens would remain (more or less) the same.
The Mean
The mean is the arithmetic average of the scores.
X_
= iXi_________N
The Mean
The mean is the arithmetic average of the scores.
The mean is the center of gravity of a distribution. DeletingBill Gates’ assets would change the national mean income.
X_
= iXi_________N
The mean of a group of scores is that point on the number linesuch that the sum of the squared distances of all scores to that pointis smaller than the sum of the squared distances to any other point.
The Mean
The sum of squared deviations from the Mean is at the lowest value.
X_
Xi -( ) 2is lowest
The Mean
The sum of squared deviations from the Mean is at the lowest value.
X_
Xi -( ) 2is lowest
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1.61.41.21.0.8.6.4
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X_
The Mean
The mean is the arithmetic average of the scores.
The mean is the center of gravity of a distribution. DeletingBill Gates’ assets would change the national mean!
The sum of squared deviations from the Mean is at the lowest value.
The mean is not a good measure of central tendency if thereare outliers.
