The mаrketing teаm аt a natiоnal streaming service is develоping a new, shоrter advertisement designed to improve customer perceptions of their value. To test its effectiveness, the researchers administer a brand attitude survey (measured on an Interval scale) to a group of 50 current customers before they watch the new advertisement, and then again to the same 50 customers immediately after they watch it.To determine if the new advertisement caused a statistically significant increase in the average brand attitude score, the researchers should use ________