When Audrina raised the price of her homemade cookies, her total revenue increased. This suggests that the demand for Audrina's cookies is elastic

Threats to internal validity of quasi-experiments include

A) failure of randomization. B) failure to follow the treatment protocol. C) attrition. D) all of the above with some modifications from true randomized controlled experiments.

Which statement best describes the relationship between steamboats, keelboats and flatboats on the Mississippi River in the antebellum period?

a. Steamboats were substitutes for both keelboats and flatboats. b. Steamboats were complements for both keelboats and flatboats. c. Steamboats were substitutes for keelboats and complements for flatboats. d. Steamboats were substitutes for flatboats and complements for keelboats.