Final answer:
If the price of pizza decreases, economists would expect Andy's demand for beer, which is a complement to pizza, to increase.
Step-by-step explanation:
When analyzing the impact of a price change for one good on the demand for another, especially in the case where two goods are complements, economists would expect certain reactions in consumer behavior. If Andy views beer and pizza as complements, a decrease in the price of pizza should lead to an increased demand for beer because the consumption of one good enhances the consumption of the other. This phenomenon reflects the reverse effect associated with the price change of complements; when the price of one complement decreases, consumers are more inclined to purchase both goods since they gain more utility from using them together.