We expect the demand for a product depends on its price: The higher the price, the lower the demand. However, this may not be entirely true. In an experiment conducted by professors at Northwestern University and MIT, a mail-order dress was available at the prices $34, $39, and $44.

The number of dresses sold weekly over a 20-week period was recorded. The prices were randomized over 60 weeks. Conduct a test to determine whether demand differed and, if so, which price elicited the highest sales.