Percentages are very useful in day to day activities and can be a handy way of writing fractions, making comparisons and describing change. For example, in a class test where a student scores 7 points out of a possible 10, and as a fraction, this is expressed as 7/10. The same can also be expressed as a percentage where the fraction 7/10 is multiplied by 100 percent. In this case 7/10*100%= 70%. Therefore, the student scored 70 percent of the total mark in the test. On the other hand, percentages can also be used to describe change. For example, if the number of people employed rose by 115,000 in 2016 from 2500,000 in 2015, then 115,000 represents an absolute change (exact value) in total employment in the year 2016. However, to find the relative change, percentages are used and in this case, the relative percentage change is found by 115,000/2500,000*100% which equals a 4.6 percent increase (relative change) in total employment (Stats.mom.gov.sg). In this way, it is more effective to use percentages to represent the relative change since few people are interested with the exact figure (absolute change) and will usually want to know the rate at which a value has increased/decreased compared to a previous value.
However, percentages are also prone to misuse when expressed as averages, when they describe shifting reference values or when they represent less than nothing. For example, when percentages are used as fractions, a student scoring 90 out of 100 points for a final test has a 90% score. However, if the results of a midterm test where the student scored 7 out of 10 points are considered, the student will have scored 70% in the midterm. The mistake would be to add both percentages 70% plus 90% then dividing the value by two to find the student’s aggregate mark, and this would result in an average percentage of 80 percent. However, this is wrong, and the student's actual score is the sum of total points scored (90 final +7 midterm) divided by the total number of points possible (100 for final + 10 for midterm) and in this case, the percentage is found by 97/110*100% which is equal to 88.18%, and this is the actual score for the student (Bowser).
Works Cited:
Bowser, S. Uses and Abuses of Percentages. 1st ed. 2014. Web. 19 June 2016. <http://mrsbowserqchs.weebly.com/uploads/1/0/9/5/10959249/3a_day1.pdf>.
Stats.mom.gov.sg. "Absolute Vs Relative Change Concepts and Definitions". Stats.mom.gov.sg. N.p., 2016. Web. 20 June 2016. <http://stats.mom.gov.sg/SL/Pages/Absolute-vs-Relative-Change-Concepts-and-Definitions.aspx>.
