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# Data meeting

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### Data meeting

1. 1. Using Basic Statistics to Look at Your Data { Data Coach Meeting: January 2014
2. 2. How did my class do?
3. 3. Mean or Median? If you want a “helicopter view” of how your class did on a test: • Use “median” in eschool if you are looking at less than 30 data points. • Use “mean” in eschool if you have 30 data points or more.
4. 4. Using the Mean If You Have More Than 1 Class You can combine means using this simple formula: (Class 1 Mean) (# of class 1 students) + (Class 2 Mean)(# of class 2 students) (# of students in both classes)
5. 5. How reliable is this test?
6. 6. Fact: All Tests Have Errors • When you give your test, eschool will give you the standard deviation. • Most teacher-made tests have a reliability coefficient of .50-.60, so assume .55. • Only well-tested tests (WISC, WJ-III) have upward of .90 reliability.
7. 7. Find the Standard Error of a Test • Standard Error is the distance from a student obtained score and their actual score based on test error. • You can figure out the standard error. Let’s assume the standard deviation was 7, and the reliability was .55 for a teacher-made test.
8. 8. Standard Error of Measurement (SEM) SEM = 11 x the square root of 1-.55 SEM = 11 x the square root of .45 SEM = 11 x .67 SEM = 7.37 *So, if a child scores a 90% on a test, they could have a true score in the range of 83 to 97. You simple add and subtract the SEM from the score they receive.
9. 9. Using SEM in Grading
10. 10. Now that you know SEM… In the previous section, we saw the standard error of measurement (SEM) give us a glimpse of how reliable a fictitious test is. It is not unreasonable to consider the SEM when determining how to use multiple measures in the classroom. The larger the SEM, the more of a need for multiple measures