What is a left sided, right sided, and two sided Fishers exact test?
Fisher’s exact test is computed by fixing the marginal totals of a 2×2 table and then determining the probability of each of the possible tables that could result in those marginal totals. The different sided tests vary in how these individual probabilities are summed into the final value produced by the test. The left sided test is recommended (see 3) since it results in a value that is easy to interpret as a measure of association between words. Rather loosely speaking, it is the probability of randomly sampling a 2×2 table where a bigram occurs less frequently than was observed in the corpus you are working with. So, a high left sided probability indicates that you are very unlikely to observe the bigram more frequently than you already have (if you took a random sample from a similar population). This suggests that the bigram is a “special” pair of words that may merit further attention. The paper “Fishing for Exactness” gives a fairly detailed description of computing left, right
Fisher’s exact test is computed by fixing the marginal totals of a 2×2 table and then determining the probability of each of the possible tables that could result in those marginal totals. The different sided tests vary in how these individual probabilities are summed into the final value produced by the test.
Fisher’s exact test is computed by fixing the marginal totals of a 2×2 table and then determining the probability of each of the possible tables that could result in those marginal totals. The different sided tests vary in how these individual probabilities are summed into the final value produced by the test. The left sided test is recommended (see 3) since it results in a value that is easy to interpret as a measure of association between words. Rather loosely speaking, it is the probability of randomly sampling a 2×2 table where a bigram occurs less frequently than was observed in the corpus you are working with. So, a high left sided probability indicates that you are very unlikely to observe the bigram more frequently than you already have (if you took a random sample from a similar population). This suggests that the bigram is a “special” pair of words that may merit further attention. The paper “Fishing for Exactness” gives a fairly detailed description of computing left, ri
