Hypothesis Testing: Before the pandemic (in 2019) average household income in city A was 60 thousand dollars per year. After the pandemic, I believe the household income has decreased significantly. I gather a sample of data of 900 households and the average income I observe in my sample is 43.5 thousand dollars, with the standard deviation of 2 thousand dollars. Do I have enough evidence to show that the pandemic statistically has changed the household income in city A?