The Kth 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
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview.
Sign up
to
access the rest of the document.
 Fall '11
 Adjunct
 Math, Harshad number, Self number, Bert G. Wachsmuth, 301.5

Click to edit the document details