Eta is another dispersion-based measure recently adapted by Du et al. (2021) for comparative analysis of two corpora. It is based on the Deviation of Proportions (DP) suggested by Gries (2008). DP is obtained by comparing the relative size of each text in a corpus to the relative frequency of a target word in each text and summing up all differences. Like Zeta, Eta therefore also measures the degree of even distribution of a feature, but it does so in a different way, namely, by comparing the DPs of words in two corpora to identify which words have a stronger dispersion in the target corpus. 


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