Percent v. percentage points

Educators may or may not enjoy mining through test data. Generally, though, if data shows an improvement over previous results, there should be a certain level of satisfaction found in processing the numbers. Of course, the converse is true as well.

Despite the results, once the data has been analyzed, it is time to share the information. In doing so, this math teacher has noticed too often the misuse of the word percent.

In the spirit of positivity, let’s say one year Algebra I was at 60% Advanced and Proficient and the next year the scores improved to 75%. We should all agree this is a 15 percentage point improvement.

It becomes a problem when we want to announce to our public a 15 % improvement when in fact it is a 25 % improvement, which, of course, is even better news.

For a quick review on calculating percent of change visit this site.

A few years ago, I was visiting the Web site of a state department of education when I noticed the misuse of the term percent. I wrote an email not unlike this post suggesting a correction. Within a few days I received a phone call from a rather annoyed employee of the referenced state department explaining to me that the Web site was written so “lay people” could understand the information. I countered I thought if those of us who knew better used the correct terminology maybe “lay people” would understand the correct usage of the terms as well.

As educational leaders, it is our responsibility to share reports with our public accurately. This is one way to ensure we do just that.


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About barbarawmadden

I began teaching in 1981, but after a few years decided staying home with my children was what was best for my family. After almost 20 years raising four children, I returned to the classroom in 2005.

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