# How to prove importance sampling ratio is uncorrelated with action-value (or state-value) estimate?

In Sutton & Barto (2nd edition), the following is mentioned on page 150 (p. 172 of the pdf), section 7.4:

the importance sampling ratio has expected value one (Section 5.9) and is uncorrelated with the estimate.

How can we prove the importance sampling ratio is uncorrelated with the estimate?