The Big Idea • More studies are better than less studies. Let me ask a question. meta.ppt Northwest CLD Dave told us that some research studies are more powerful than others. I was wondering if there is any procedure in education that examines collections of studies? meta.ppt I am glad you asked that question. There is a procedure for ‘aggregating*’ data from a variety of Meta-Analysis studies. It is called meta- analysis. *Aggregate: To gather into a mass or whole. meta.ppt In meta-analysis, a researcher examines many studies on a particular strategy and derives a numerical indicator of the relative effectiveness of the strategy, averaged across all studies. This indicator is called an 2 effect size (ES). Such an analysis of research not only provides a numerical indicator of the relative effect of a particular intervention, but the effect size also allows comparison with other approaches used in special education or related services. Thanks NWCLD presenters. We ARE getting a lot of great evidence based practices from a research-summary procedure called meta-analysis. Check out what Steve 1 Forness and his buddies wrote in Teaching Exceptional Children… I heard something about this ‘ES’ in another special education class. Could you review how this works. 3 meta.ppt I’d love to. Let’s begin with what you know about the ‘normal bell-shaped curve since it is at the heart of summarizing studies. First, what does the curve look like? meta.ppt I hope I get the right answer: “It looks like a bell.” meta.ppt Let’s talk about a normal distribution – the bell-shaped curve. The peak of the distribution, which occurs at the ‘mean’ (the average of all the numbers).. meta.ppt Cite examples. Math performance, IQ, shoe size. Each side of the curve has inflection points where the curve makes shifts in direction. meta.ppt Each side of the curve has inflection points where the curve makes shifts in direction. meta.ppt Inflection points occur at very specific places. Mean meta.ppt The first inflection point to the right of the mean occurs one ‘standard deviation’ (SD) above the mean. 1 SD Mean Mean + 1 SD Below Above meta.ppt The second inflection point to the right of the mean occurs two standard deviations above the mean. Mean Mean Mean + + 1 SD 2 SD Below Above meta.ppt Inflection points below the mean also occur at one and two standard deviations below the mean. Mean Mean Mean Mean Mean - - + + 2 SD 1 SD 1 SD 2 SD Below Above meta.ppt Because all points are in reference to the mean, we will indicate the differences with the mean implied. -2 -1 Mean +1 +2 SD SD SD SD Below Above meta.ppt One of the most useful aspects of the normal curve is that there are specific areas under each part of the curve. -2 -1 Mean +1 +2 SD SD SD SD meta.ppt As we can see, 50% of the data (Math scores, IQs, shoe sizes) fall on each side of the mean. 50% 50% -2 -1 Mean +1 +2 SD SD SD SD meta.ppt Of this 50%, 34% falls between the mean and one standard deviation above and one standard deviation below the mean. 50% 50% 34% 34% -2 -1 Mean +1 +2 SD SD SD SD Below Above meta.ppt The area between one and two standard deviations from the mean holds 14% of the distribution. 50% 50% 34% 34% 14% 14% -2 -1 Mean +1 +2 SD SD SD SD Below Above meta.ppt Since the total area on each side must total 50%, we know there is 2% of the distribution beyond two standard deviations (SD) in each direction. 50% 50% 34% 34% 14% 14% 2% 2% -2 -1 Mean +1 +2 SD SD SD SD Below Above meta.ppt Generally, the ‘average range’ is considered between -1 and +1 standard deviations (SD). 50% 50% 34% 34% Average Range 14% 14% 2% 2% -2 -1 Mean +1 +2 SD SD SD SD meta.ppt Here I am back at Diamondhead. Now that you can see characteristics of the bell-shaped curve, please take out the copy you received earlier. How about now. Let’s mix a break with Thanks for the handout, Dave. a job. Tell your neighbor what How soon can we break? percentile ranks begin and end the meta.ppt ‘average range.’ Discovery learning. The Curve meta.ppt Note: Other Bell-shaped Curves meta.ppt Back to Meta-Analysis Recall the description of meta-analysis. • In meta-analysis, a researcher examines many studies on a particular strategy and derives a numerical A indicator of the relative effectiveness of the strategy, averaged across all studies. This indicator is called an effect size (ES). Such an analysis of research not only provides a numerical indicator of the relative effect of a particular intervention, but the effect size (ES) also allows comparison with other approaches used in special education or related services. B or C • Suppose we had an intervention like giving vitamins (A) that was being compared to either another intervention (B) like giving candy, or no treatment (C). • Suppose that the groups who received vitamins (A) and the groups who received (B) “candy” or (C) “nothing” performed equally at the start on a math test. meta.ppt Further, suppose that we monitored the progress of both groups over time, and the treatments were provided with fidelity. A Math Scores The two collections B or C of groups Math Scores are equal. +1 +2 +3 Now Month Month Month Time meta.ppt Further, suppose that we monitored the progress of both groups over time, and the treatments were provided with fidelity. A Math Scores After one month, we B or C see this Math Scores pattern. +1 +2 +3 Now Month Month Month Time meta.ppt Further, suppose that we monitored the progress of both groups over time, and the treatments were provided with fidelity. A Math Scores After two months, we B or C see this Math Scores pattern. +1 +2 +3 Now Month Month Month Time meta.ppt Further, suppose that we monitored the progress of both groups over time, and the treatments were provided with fidelity. A Math Scores After three months, we B or C see this Math Scores pattern. +1 +2 +3 Now Month Month Month Time meta.ppt If this was the result, which method would you choose to use in your classroom, A, B, or C? A Math Scores B or C Math Scores +1 +2 +3 Now Mont Mont Mont h h h Time meta.ppt By drawing a line along the mean (0 SD) we can see that method A’s mean is actually 1 SD higher than the B and C. A Math Scores B or C Math Scores +1 +2 +3 Now Month Month Month Time meta.ppt By drawing a line along the mean (0 SD) we can see that method A’s mean is actually 1 SD higher than the B and C. A Math Scores B or C Math Scores +1 +2 +3 Now Mont Mont Mont h h h Time meta.ppt Effect size (ES) is based on aggregated data A Math Scores When several studies create the B or C Math Scores pattern we see here, we are more confident that the results are trustworthy (valid). +1 +2 +3 Now Month Month Month Time meta.ppt Effect size (ES) is based on aggregated data A Math Scores Since the performance of group B or C Math Scores A is +1 SD beyond group B or C, we say that method A (giving vitamins) has an effect size of +1. +1 +2 +3 Now Month Month Month Time meta.ppt Is it always an even number like 1, 2, 3? The answer is ‘no.’ Effect sizes can be fractions (e.g., ES = +.5 (half an SD) or ES = +.35). It could also be negative (ES = -.6). Generally ESs that are worth paying attention to as a teacher are +.40 or higher. The highest EF that I know is 1.62 for using mnemonics as an instructional tool. Any questions from the class? meta.ppt Summary • Meta-analysis aggregates data from several studies that deal with a particular treatment. • The number that describes how well the treatment works is called effect size (ES). • ESs can be positive (+) or negative (-). • Generally the bigger the ES for the treatment, the more you can take it to the bank. • Distribute Forness’ article on meta-analysis • Display some sources of information that are based on meta-analysis. meta.ppt

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