Final answer:
The most relevant indicator for evaluating if customers are paying attention to email newsletters is an increased rate of coupon redemption directly offered through the newsletters. The correct answer is a) Customers redeem store coupons 25% more often.
Step-by-step explanation:
To evaluate whether customers are paying attention to our email newsletters, we would look for indicators related to engagement and direct actions resulting from those emails.
This indicator shows that customers are actively engaging with the store's promotions and offers, which would suggest that they are indeed paying attention to the email newsletters.
The provided options discuss various outcomes, but the most relevant indicator to the question at hand would be something that shows a direct interaction with the email content itself, such as an increased rate of coupon redemption that is directly offered through the newsletters.
Therefore, answer (a) Customers redeem store coupons 25% more often, directly addresses this, as it likely implies that the newsletter content is being read and acted upon by the customers.