Your null hypothesis should identify the statistical test you are planning to use. If it says "There are no significant differences between these categories"- it's chi-squared.
What does O represent?
The results you observe in the investigation.
What does E represent?
The results you expect.
How do we interpret our chi-squared results?
Our calculated value of chi-squared is larger/smaller than the critical value of chi-squared for P=0.05.
There is a greater/less than 5% probability that the differences (between the observed and expected data) are due to chance.
