Someone criticizes the study saying "we can’t tell if additional sales were due to the poster." Is this a valid criticism of the study?

Question

record company would like to see if sending out posters of a popular artist can generate orders for the artist's records. They choose a large sample of potential customers and randomly send half of them a poster of one of their popular artists along with a catalog, while they send only a catalog to the other half. They observe

that more orders come from the first group for the music of the artist on the poster than the second group. They conclude that sending the poster is generating additional sales.

Answer 1

One thing that is stressed in statistics is that correlation doesn't mean causation. When trying to justify a causation statement, all other possible factors that might influence the outcome need to be tightly controlled.