Final answer:
Economists deal with the problem of many factors changing in a market by conducting a market study.
Step-by-step explanation:
When analyzing a market, economists deal with the problem of many factors changing at the same time by conducting a market study. This study involves gathering and analyzing data on various factors such as consumer behavior, competition, market trends, and economic indicators. By carefully studying these factors, economists can identify patterns and make informed predictions about the market's future.