A company's marketing team tells an analyst that fewer customers are opening emails in the recent email campaign. The analyst interviews a few marketing coordinators and discovers changes were made to the email subject line between the last successful email campaign and the recent one. The analyst then uses a statistical technique to compare the email open rates for each campaign. Which step does the comparison of the email open rate represent in the plan-do-check-act cycle?

-act

-do

-check

-plan