Percentage vs. Percentile
When we say "Percent" we are really saying "per 100". It is a number or ratio expressed as a fraction of 100. Percentile refers to the percentage of scores that are equal to or less than a given score.
Say a student takes a test made up of 40 questions and answers 34 of them correctly. The percentage of correct answers, or score, is the number of correct answers divided by the total number of questions, multiplied by 100. So, 35 ÷ 40 = 0.85. 0.85 × 100 = 85. The student got 85% of the questions on the test correct.
In the case of national norm scores, such as those provided as a reference on the easyCBM system, this refers more specifically to the percentage of scores in the national norm sample that are equal to or less than the score your student received.
For example, for Grade 3 CCSS Rdg, a score of 23/25 is the 50th percentile rank. A score of 24/25 is the 75th percentile rank, etc.
Our progress monitoring scoring guidelines are derived from the number of students who score at or below a particular score on a test. These numbers are based on what is called a ‘percentile rank’. Roughly speaking, these numbers indicate the proportion of students at that grade level that your students’ scores are equal to or above. In other words, how does your student ‘rank’ among other students in the same grade?
Our easyCBM district users, nation-wide, generate these scores from their students who’ve taken on-grade measures that are administered 3 times a year (fall, winter, and spring). To know how a student compares to other students in their grade (at one of three benchmark times of year) take a students score from a measure and compare it to the same measure, grade, and time of year the test was taken. Ideally, a student score should fall at the 50th percentile for them to be considered performing on grade. If they are at the 50th percentile or above, no other testing in that area is needed until the next benchmark testing cycle. If they fall below the 50th percentile, then progress monitoring measures should be implemented.
If you login to your account and go to the Reports tab you’ll notice two documents for download, located in the upper right hand corner of the gray Reports and Analysis box, called Progress Monitoring Scoring Guidelines and Detailed Percentage Table.
Looking at the current Progress Monitor Scoring Guidelines, the way you figure out what percentile rank ‘goes with’ a particular score is:
- Find the measure you are interested in,
- Find the grade you are interested in,
- Find the “benchmark” season you are interested in,
- Find the “score” you are interested in (4th column in) or the “Percentile” you are interested in and
- Look up the ‘Percentile” (if you were trying to figure out what specific percentile rank goes with a particular score) or
- Look up the ‘Score’ (if you were trying to figure out what specific score goes with a particular percentile rank).