Percentile Calculator
Answer:
The 90th percentile is: 257
Solution:
In this problem, you want to find the 90th percentile in the data set. At least 90% of the data values will be less than this number.
Take note that there are 12 data values in this data set. Therefore, $N = 12$.
We need to sort them in ascending order.
$ 100, 120, 176, 180, 189, 200, 222, 226, 235, 237, 257, 284 $
The index of the sorted data set represents the position. The first number, 100 has an index of 1, the second, 120 has an index of 2, etc. To find the index of the 90th percentile, apply the formula $$ i = \frac{p}{100} \cdot N $$
where i represents the index. Substituting in the values for this problem, we have $$ i = \frac{90}{100} \cdot 12 $$ $$ i = 10.8 $$
If i were an integer, the percentile would be found by taking the average of the data values at positions i and i + 1 in the sorted data set. Since i is not an integer in this problem, we round i up to the nearest whole number. $$ i = 11 $$ Counting 11 data values in the sorted data set from the beginning, the data value at position 11 is 257.
Therefore, the 90th percentile is: 257