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Can someone help me understand these stats about homeschooling?


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Hi Cyndi,

The figure they use is more for a lay person's benefit than a statistically accurate one. I think that is why they put the footnote that they did but I am guessing there would be a more thorough explanation in the original article if you went there. I think they are trying to show that the average public student (hence 50%tile) is consistently outperformed in each subject by "so many" %tile points and the figure they used was the easiest way to do that and presented the most dramatic picture.

In a nutshell, from their figure, the average homeschool student consistently performs better in each subject than the average public school student.

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I'm not sure, but think it is simply the average of so many public school students. Ruth Beechick explains standardized test scores pretty well in her book, You Can Teach Your Child Successfully.

 

She states that "No student ever rates a percentile rank of 100, because you could not say a student scored higher than 100% of all students. The highest score possible on this kind of scale is 99.

Twenty percent, or one-firth of all children in a grade, rank between the 40th and 59th percentiles. Half of all children rank between the 23rd and 76th percentiles. This large group can be lumped together and thought of as the average group of children. "

Clear as mud??:001_huh:

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but for all of them to be 50%, i'd say they used the normed %. for example, a test is given to groups of students (before it's released to be used on a large scale). they use that data to determine what the "average" first-grader, etc. should score on that particular test. so when a ps student takes an achievement test and they get results back that say your child is at the 85% in math, that means they scored higher than 85% of the students in that original group. so it looks to me like they are doing the same thing with the homeschool data; comparing the hs kids to that original group. they're not comparing the hs kids to actual current ps performance. i would think you should be able to get district or state averages on achievement tests and use that as a direct comparison. it's been a long time since that educational tests and measurements class!

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On a standardized test, the 50th percentile is by definition the average score. The tests are scored on a bell curve relative to how the entire group did, not according to how many each individual person got right or wrong. However, the bell curve is created based on a particular year, then re-normed every couple of years. So the 50th percentile might not be the dead on average for this year, but it's going to be close based on average performance a few years ago.

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