A marketer wants to know which of two different video lengths drives a stronger CPA for their campaign. To do this, what should they set up?
Correct Answer
A Demand Gen Experiment
Why is this the correct answer?
They should set up a Demand Gen Experiment. An experiment splits traffic between two variants at random, so the two video lengths run against comparable audiences at the same time and the difference in cost per acquisition can be attributed to the creative rather than to timing, seasonality or audience differences. That is what makes it a test rather than a comparison. Running the two lengths in separate ad groups, the tempting alternative, is not a controlled test: delivery is decided by the system, budget flows unevenly, and the audiences overlap, so any difference in CPA has several possible explanations. Experiments also report statistical confidence, which is what prevents a team from acting on a difference that is really just noise.
Why are the other options wrong?
A new ad group
A new ad group runs both lengths in the same campaign without random assignment or controlled measurement, so the result is not a fair test.
A Search Lift study
A Search Lift study measures additional searching driven by a campaign, not the relative CPA of two creatives.
A brand survey
A brand survey measures attitudes rather than cost per acquisition.
Real-world example
A subscription brand tests a 15-second cut against a 30-second cut in a Demand Gen Experiment. The shorter version wins on CPA by 22% with high confidence, and the longer cut is retired — a result the team's previous side-by-side ad groups had suggested the opposite of.
Topics in this question
About the Google Ads Video Certification
The Google Ads Video Certification is about using YouTube and Google video inventory at every stage of the funnel: picking the right campaign subtype and ad format for awareness, consideration or action, applying creative best practice, and proving impact…
Exam guide and all 456 Google Ads Video questions →Related Google Ads Video questions
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