A Statistic that Can’t Be Ignored

Reading academic studies with lots of statistics is never a great deal of fun for me, but over the last several weeks, I’ve repeatedly been bombarded with one group of statistics that is difficult to ignore, in large part because it corroborates the anecdotal evidence from my own classroom experiences.  If you are not a numbers person, bear with me.  The end result is worth it, I think.

First, let me refresh your brain on what is meant by effect size (ES). An ES tells you how many standard deviations larger (or smaller) the average score for a group of students who were exposed to a given strategy is than the average score for a group of students who were not exposed to a given strategy.  Therefore, an ES essentially tells you just how important or influential a strategy is, and the larger the ES, the more influential the strategy is to student learning.  ESs are actually usually quite small numbers, but small ESs translate into large percentile gains.  So an ES of .66 in one study translated into a 25 percentile point gain (Tenenbaum and Goldring, 1989).

Okay…so that brings us to the statistic that can’t be ignored.  Two researchers, Hattie and Timperley (2007), aggregated 196 studies and 6,972 ESs on the role of feedback on student learning. (Feedback consisted of formal and informal formative assessments that informed the student and teacher about how to best improve student learning.)  They calculated an overall average ES of 0.79 for feedback, which translated into a 29 percentile point gain!  To be sure, this is an overall average, meaning some studies showed smaller ESs, but it also means some showed larger ESs.  Other independent studies corroborate the findings of Hattie and Timperley.

Now, to get those gains, feedback needs to be what is considered “positive” rather than “negative.”  Negative feedback simply involves making comments like “Good job,” or “Needs improvement,” without explaining to the students what exactly they’ve done well or exactly what they need to change to do better.  Effective feedback must be detailed and specific to positively influence student learning.

Next year, a major focus for my school is assessment – formative, summative, authentic, alternative, etc.  Over the next several weeks, as I research these things more and more, I’m going to post more about feedback, formative assessment, and how to use both to enhance student learning.  Since it appears to be so influential to student learning, it’s something every teacher needs to understand and use well.  And I’m putting myself on the top of that list!





  1. Pingback: A Few More Thoughts on Feedback and Assessment | Wiser Today and Still Learning

  2. Pingback: Thoughts on iSummit 2013 | Wiser Today and Still Learning

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