T-score expresses the certainty with which we can argue that there is an association between the words, i.e. their co-occurrence is not random. The value is affected by the frequency of the whole collocation which is why very frequent word combinations tend to reach a T-score high value despite not being significant as collocations.

In most cases, T-score is more reliable or more useful than MI Score.

see Concordance – collocations
see Statistics in Sketch Engine

compare MI Score