Final answer:
The [EW] in the utterance indicates a correction of the verb tense.
Step-by-step explanation:
The [EW] in the utterance 'We is[EW:are] go/ing to Grandma/z' indicates a correction of the verb tense.
When the sentence is properly written, it should be 'We are going to Grandma's.'
The [EW] indicates that 'is' should be corrected to 'are' to match the subject 'we'.