Inquiry about the indices in TAALES2.8.1

[Lujie Zheng]

     Hi，Recently, I have used TAALES 2.8.1 to calculate the frequency and association strength of different types of bigrams (e.g. Adj+N bigram, N+N bigram) , using COCA Academic Index. However, I have found a question, which is that the index number for the bigrams in TAALES are not the same as those shown in https://www.english-corpora.org/coca/. Taking the N+N bigram "defense capability" as an example, In TAALES, the frequency score is 0.505884917 and the MI score is 4.19785349959. However, when I calculate it using the COCA website (Academic subcorpus) , it shows that the frequency score is 15 and the MI score is 6.73.  And also, as shown in TAALES result, some bigrams do not have frequency and association strength scores, but when I search them in COCA website, they do have. Taking the N+N bigram "transaction process" as an example, the frequency and association strength for it are N/A in TAALES results, but in COCA website (Academic subcorpus), the frequency is 3 and the MI is 2.7.

      I am a little bit confused about why these differences exist. And whether I can get some answers for these?

     Thank you.