John Hattie is a professor at the University of Melbourne, Australia. He is famous for a book, Visible Learning, which claims to review every area of research that relates to teaching and learning. He uses a method called “meta-meta-analysis,” averaging effect sizes from many meta-analyses. The book ranks factors from one to 138 in terms … Continue reading John Hattie is Wrong
One of the best things about living in Baltimore is eating steamed hard shell crabs every summer. They are cooked in a very spicy mix of spices, and with Maryland corn and Maryland beer, these define the very peak of existence for Marylanders. (To be precise, the true culture of the crab also extends into … Continue reading Meta-Analysis or Muddle-Analysis?
One issue I hear about all the time when I speak about evidence-based reform in education relates to the question of programs vs. practices. A program is a specific set of procedures, usually with materials, software, professional development, and other elements, designed to achieve one or more important outcomes, such as improving reading, math, or … Continue reading Programs and Practices
In researching John Hattie’s meta-meta analyses, and digging into the original studies, I discovered one underlying factor that more than anything explains why he consistently comes up with greatly inflated effect sizes: Most studies in the meta-analyses that he synthesizes are brief, small, artificial lab studies. And lab studies produce very large effect sizes that … Continue reading “But It Worked in the Lab!” How Lab Research Misleads Educators
If you ever go into the Ripley’s Believe It or Not Museum in Baltimore, you will be greeted at the entrance by a statue of the tallest man who ever lived, Robert Pershing Wadlow, a gentle giant at 8 feet, 11 inches in his stocking feet. Kids and adults love to get their pictures taken … Continue reading Effect Sizes and the 10-Foot Man
Ever since Gene Glass popularized the effect size in the 1970s, readers of research have wanted to know how large an effect size has to be in order to be considered important. Well, stop the presses and sound the trumpet. I am about to tell you. First let me explain what an effect size is … Continue reading What Is a Large Effect Size?
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