1. 查統計書本中有關卡方檢定的限制條件 ()
2. 網路上查找Pearson's chi-square test (i.e., Wikipedia) http://en.wikipedia.org/wiki/Pearson's_chi-square_test
其中的assumptions那一段
The chi square test, when used with the standard approximation that a chi-square distribution is applicable, has the following assumptions:
a. Random sample – A random sampling of the data from a fixed distribution or population.
b. Sample size (whole table) – A sample with a sufficiently large size is assumed. If a chi square test is conducted on a sample with a smaller size, then the chi square test will yield an inaccurate inference. The researcher, by using chi square test on small samples, might end up committing a Type II error.
c. Expected Cell Count – Adequate expected cell counts. Some require 5 or more, and others require 10 or more. A common rule is 5 or more in all cells of a 2-by-2 table, and 5 or more in 80% of cells in larger tables, but no cells with zero expected count. When this assumption is not met, Yates' correction is applied.
d. Independence – The observations are always assumed to be independent of each other. This means chi-square cannot be used to test correlated data (like: matched pairs, panel data). In those cases you might want to turn to McNemar's test.
原帖由 pighead 於 30/5/2011 12:09 發表
about point c
in your chi-square test (so called goodness of fit), all the cells fit the expected count?
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Yes, if the cells fit the criteria, we used Chi sqaure test otherwise we used Fisher's exact test.
Moreover, the subjects were tested for different diseases albeit the samples are derived from the same set of subjects. the data still could be treated as independnet variables.
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發表於 2011-5-27 19:47:03
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發表於 2011-5-28 11:55:53
