To compare three packaging designs for a new food, a manufacturer randomly selected three grocery stores in each of 50 cities. The three designs were randomly assigned to the three stores in each city, and sales were compared for a 2-month period. What is the largest population you think the results can be extended to? all grocery stores in cities similar in size to these 50 all grocery stores the manufacturer currently sells to all grocery stores worldwide all grocery stores in these 50 ci