Some Musings on Metrics

Greetings again. I hope that all is going well for you.

At my university, the semester will end soon. Therefore the students are doing course evaluations. The students rate various aspects of the teaching. After the semester, we teachers receive our sets of ratings. We also receive an overall mean score for each course.

For some reports on our performance, we provide only the overall means. These single scores are somewhat helpful. But they don’t say which aspects the students perceived as weak or strong. They also don’t reflect the aspects that students aren’t qualified to rate.

Some other single metrics likewise have limitations. Body mass index (BMI), which is based on height and weight, suggests whether someone weighs a suitable amount. But someone muscular may have a high BMI but not be fat.

Likewise, readability scores based on word lengths and sentence lengths give a general sense of whether a piece of writing is easy to read. But writing with a good readability score can be hard to read if it is not logical or if information is missing.

Impact factors are somewhat analogous. They reflect how much, on average, articles in the journal are cited. Highly cited journals tend to be of high quality. But they're not the only good journals. And they're not always the most suitable site for a paper. Other aspects also must be considered when deciding where to publish.

In short, the quality of a complex item can’t be reduced to one number. Such numbers can help us to notice some important aspects. But they’re not the whole story.

Until the next post—

Barbara