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Rebecca Birch's avatar

I had my popcorn out. It was fun to be surprised by this quirk of programming.

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John Wills Lloyd's avatar

It is difficult, indeed, to interpret the data from a time series. And, once one "leave[s] the world of controlled experiments and enter[s] the world of policy," the arguments can be predicated on very different beliefs. So, with the data you showed, one can argue just about anything: "The world is flat!" "Oh, no it's not. It's round!"

The methods of single-subject (or "-case," if one prefers) research allow one to do so, but they require many more measurement occasions and rigorously controlled comparisons between two levels of an independent variable. In fact, those are experimental methods, too.

BTW, the US report of the "National Reading Panel" included a meta-analytic comparison of synthetic and analytic phonics. Both were more effective than the control condition (essentially, "whole language"), but the average effect size for synthetic phonics was not statistically significantly greater than for analytic phonics. I should publish my slides about this comparison...sigh.

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