An eCommerce brand wants to validate its YouTube investment by tracking how ads influence customer sentiment regarding purchase intent. Which tool should they use?

They should use Brand Lift studies. Brand Lift measures the effect of advertising on what people think, not just what they click, by comparing survey responses between a group exposed to the ads and a control group that was not. The difference between them is the lift attributable to the campaign, across metrics such as ad recall, brand awareness, consideration, favourability and purchase intent — the last being exactly what this brand wants to validate. That matters for YouTube specifically, because video often does its work well before any click: someone who watches a product story may search for the brand a fortnight later, and click-based reporting will credit that search. Brand Lift provides the evidence that the video changed attitudes in between, which is how upper-funnel investment gets justified rather than assumed.