Write a simple research question that can be answered with an independent samples

what was the margin of error for this study?

A marketing agency wanted to determine if a new commercial changed people's opinion about a company. They recruited n=30 participants to watch the commercial. First, everyone was givien a survey to determine their attitudes toward the company. Then, everyone watched the new commercial. Finally, they were given the same survey again and asked about their attitudes toward the comapny after seeing the commercial. The agency wanted to see if attitudes were changed by the commercial. What statistical test should they use?

How do you calculate a sample statistic and p-value (Not sure if this helps, but we are told to use statkety to help generate our answers)?