The Mutual Information score expresses the extent to which words co-occur compared to the number of times they appear separately. MI Score is affected strongly by the frequency, low-frequency words tend to reach a high MI score which may be misleading. This is why Sketch Engine allows setting a frequency limit so that low-frequency words can be excluded from the calculation.
When comparing the T-score and MI score, in most cases T-score is more useful than MI score. However, both of these scores are affected by the corpus size. This makes them less useful when working with modern mutli-billion-word corpora. This is why Sketch Engine prefers the LogDice score in most situations, especially in word sketches.
see Concordance – Collocations
see Statistics in Sketch Engine