I have different Delta Pi unidirectional scores of Past Perfective - verb lexemes attraction and reliance relative to L2 Italian learners' oral interviews spanning many months. Ellis (2012, p. 28) points out that an
association score such as ΔP is a scale, not a test of significance with a threshold
value. Still I need to compare different Delta Pi values over time. Do you think that any test indicating the significance of difference between scores is of no use? In case you disagree, which test would you use?