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9. Weighted mean and Percentile.notebook March 27, 2014 Stascal Measures To find the position of a score with a specific percentile: • if n x p is a whole number, the position is the mean of n x p and (n x p) +1 • If n x p is a decimal, round up to find the position of the score. Stascal Measures Percentile and Percentile Rank • Percentile: a number between 1 and 99 indicating the percent of the population with a score less than or equal to a specific value • Percentile rank: the percent of the population with a score less than a specific score Ex. The table give scores for a project, ranked lowest to highest. a) determine the percentile rank for each i) 14 ii) 11 b) which score is in each percentile? i) 75th Calculating percentile rank: ii) 95th SCORE 5 8 9 11 11 11 13 14 16 17 18 19 RANK 12 11 10 9 8 7 6 5 4 3 2 1 1. sort the scores from least to greatest 2. use the formula: p ­ percentile rank L ­ number of scores less than the particular score E ­ number of scores equal to itself n ­ total number of scores *Percentile ranks are usually rounded to the nearest whole number. Oct 2­7:23 AM Oct 2­7:23 AM Stascal Measures Weighted Mean • a mean in which each component has a different weighting factor • to calculate a weighted mean, 1. convert any scores to decimals Homework p. #2,4,8 (Just for Foster) 2. multiply each score by its weight factor 3. add all values Ex. Calculate the overall percent for the following student weight factor category quiz quiz 1 (15%) assignment (15%) mark (out of 30) in­class assignment decimal X weight factor 40 (out of 60) test unit test (25%) (out of 120) ISU independent study (15%) decimal 24 89 43 (out of 60) final exam exam (30%) (out of 90) 72 Oct 2­7:23 AM Mar 26­1:35 PM Mar 26­2:00 PM 1