An example we cite from WIKI (https://en.wikipedia.org/wiki/Chi-squared_test).

We randomly select 230 residents from two neighborhoods: A and B. There were defined as white collar and blue collar based on their income. Among them, we found 150 are white collars and 80 blue collars. Among 150 white collars, 90 of them live in neighborhood A. And 50 Blue collars live in neighborhood B.

1. Construct the contingency table
2. Calculate and compare whether there is a difference between the percentages of people who live in neighborhood A by white collar and blue collar
3. Test whether living in which neighborhood depends on that status of white collar or blue collar; or test whether two variables are related or dependent on each other
   1. Write the test hypotheses
   2. Calculate chi-square test statistics and compare it to the critical value (show your work, you do not need to find the p value)
   3. State your conclusion (make sure you answer the question based on the hypothesis
4. If the test is significant, Calculate, report and interpret the OR by assuming it is case control study