Lesson 5

In Self-Check 1 you used Percentile Explorer to determine the percentile rank of Hugo, depending on the total number of people and how many people Hugo is taller than. In Self-Check 2 you will look at how a percentile rank is different than an independent percent score.

 

Self-Check 2

 

Mr. Kaupp has a student, Keisha, in his automotives class who currently has a grade of 71%. He calculates that she has a percentile rank of 83. What do these two numbers mean and why are they different?

 

Both numbers given in this scenario are measured out of 100. However, they have very different meanings when you consider what data and information they are being compared to. Let’s investigate this further.

 

Keisha’s mark of 71% in the course means that for every 100 marks, she has earned 71 of them, resulting in This percentage is based on and compared to her performance on the test and how many questions out of 100 she answered correctly.

 

Since percentile rank represents the percent of data points below a given value, Kiesha’s percentile rank of 83 means that 83% of her classmates scored lower than her. The percentile rank is based on and compared to her performance as well as the number of students who scored below her.

 

Her percentile rank of 83 is dependent on the scores of her classmates, whereas her grade of 71% is solely dependent on her performance.

 

1. What would Keisha’s percentile rank be if there were 18 students in her class and 13 of her classmates scored below her? Answer
2. What would Keisha’s percentile rank be if there were 33 students in her class and 11 of her classmates scored above her? Answer
3. As a student, would you prefer having your percentile rank or your independent percent score reflected on your progress report? Provide an explanation for your choice. Answer

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In Self-Check 2 you may have found that a percentile rank may be better to use on your progress report when you are doing better than the other students in your class. If your independent mark is not better than many students in your class, you may prefer to have your independent mark on the progress report. In the next Self-Check you will look at how percentile rank can be used in health care.

 

Self-Check 3

 

In the first year of life, the height and weight of babies are tracked very closely by health professionals. To compare one child to the average Canadian range, a health professional will use growth charts that use percentile rank.

1. Richard takes his two-month-old son to be measured at the doctor’s office. His son measures 59 cm long. What percentile rank does Richard’s son fit into at two months of age? Answer
2. At six months of age Richard’s son measures 66 cm. What percentile rank is his son in now? Answer
3. The doctor notes that the child’s percentile ranking has changed. What does this mean? Answer