Tópicos: Percentis e filas de percentis

Percentiles

In an earlier lesson, we learned about the median and quartiles in box and whisker plots. In the next lesson, we'll learn about stem and leaf plots. This lesson will cover percentile rank.

A percentile tells us what percent of values in a data set are at or below a given number.

Whenever you take the SAT the ACT, you'll most likely get your score as a percentile.

You use this formula to calculate the percentile rank of a given data value,

Let's try an example.

Before you attempt to calculate percentile ranks, you need to put your values in order. Remember, we did the same thing when we calculated median and mode!

(Video) Percentile Rank

by Joel Frederickson

This video by Joel Frederickson covers percentile rank.

$\large{\text{Summary}}$

The percentile rank of a data point is the percent of data that is equal to or less than that point.

For instance, if you are in the $40th$ percentile for your SAT score, $40\%$ of test takers got your grade or lower.

We can calculate the percentile rank with the following formula:

$$\text{Percentile Rank} = \frac{B+0.5E}{n}\cdot 100$$

Where:

$B=$ number of values below the data point

$E=$ number of values equal to the data point

$n=$ total number of values

Percentile Rank

Percentile rank (of a score) lets us know the percentage of the scores in the frequency distribution that are less than the given score. The higher the percentile rank, the better the score!

Here is an alternative formula for percentile rank: $$\text{percentile rank =}\frac{C-(0.5E)}{n}*100$$

$$\begin{align} C &= \# \text{ of values less than or equal to the data point}\\ E &= \text{ frequency of the data point}\\ n &= \text{ total } \# \text{ of values} \end{align}$$