An expected proportions chi-square, investigating Hollywood ethnic representation vs. USA IRL data

I came across a Reddit post in which a user did a quick-and-dirty data collection of the ethnicities of the three top-billed actors in each of 100+ million USD-earning movies between 2022 and 2025. They then compared the data to US census data. Regardless of how Reddit reacted, I saw this and decided that it would make a good example for explaining and performing a chi-square with expected…