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MTH 120 - Percentiles

# MTH 120 - Percentiles - The K-th Percentile is that number...

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The K-th Percentile is that number such that K % of all data values are less and (100 - K) % are larger than it, or to be more precise, at least K% of the sorted values are less than or equal to it and at least (100 - K) % of the values are greater than or equal to it. 1 The Kth percentile is any value such that at least K% of the data is less than or equal to the value. 2 Find the 40 th percentile. 0 1 1 3 17 32 35 44 48 86 87 103 112 121 123 130 131 149 164 167 173 173 198 208 210 222 227 234 245 250 253 265 266 277 284 289 290 313 477 491 Now we can do our calculations, where N = 40 (number of values in our data set). 40th Percentile: 0.4 * 40 = 16, so the 40th percentile is (130 + 131) / 2 = 130.5 Find the percentile that corresponds to a value. In other words, determine how many values are less and how many values are larger than the particular value. To find the percentile that corresponds to a particular data value x is: Percentile value of x = (number of values less than x) / (total number of values) * 100 Example Suppose you took part in the above study of cotinine levels, and your personal cotinine level was 245. What is the percentile value of 245, and how many people in the study had

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