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Unformatted text preview: Chapter 3 Describing Data with Graphs Refreshing our memories Terms you should know Frequency Distribution Relative frequency distribution Cumulative frequency distribution Percentile, percentile rank. Apparent Limit vs. Upper Real Limit Apparent Limits This is what you actually label as the class interval Real Limits of a class interval are located at the midpoint of the gap between adjacent class intervals of unit of measurement below the lower boundary and of unit of measurement above the upper boundary To calculate: divide the unit of measurement in half, subtract this number from the lower boundary of a class and add it to the upper boundary of a class No observed scores ever fall directly on a real limit, because we calculate real limits by taking half the smallest unit of measurement Group Frequency Distribution Cumulative Fr equency Distr ibution of Speeds of 25 Car s Speed (mph) f Cumulative f Cumulative Per cent (%) 9599 1 25 100 9094 2 24 96 8589 2 22 88 8084 4 20 80 7579 4 16 64 7074 4 12 48 6569 4 8 32 6064 2 4 16 5559 1 2 8 5054 1 1 4 Total 25 Cumulative Percentage Cumulative frequency: the sum of frequencies for this class interval and all intervals below Cumulative percentage: percentage of all observations which scoring the upper apparent limit or below Cumulative percentage: percentage of all observations which scoring below the upper real limit of this interval Group Frequency Distribution Cumulative Fr equency Distr ibution of Speeds of 25 Car s Speed (mph) f Cumulative f Cumulative Per cent (%) 9599 1 25 100 9094 2 24 96 8589 2 22 88 8084 4 20 80 7579 4 16 64 7074 4 12 48 6569 4 8 32 6064 2 4 16 5559 1 2 8 5054 1 1 4 Total 25 Percentile Per centile a score below which a specified percentage of observations in distribution fall For grouped cumulative frequency distributions, we often use the upper real limit of a class interval as a percentile point 8 Percentile Ranks Per centile Rank Just another way to look at percentiles: What percentage of scores lie below a given score value? The percentage of observations falling below a given point to describe the relative position of a score within the distribution Commonly used for standardized tests (SAT, ACT). I f the percentile rank for your score is 67(%), that means 67% of the total testtakers score lower than you Group Frequency Distribution Cumulative Fr equency Distr ibution of Speeds of 25 Car s Speed (mph) f Cumulative f Cumulative Per cent (%) 9599 1 25 100 9094 2...
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This note was uploaded on 04/29/2010 for the course PSYCH 1167 taught by Professor Bingshi during the Spring '10 term at Temple.
 Spring '10
 BingShi

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