Explain the difference between observed frequency and expected frequency as it relates to Chi-Square test.

Step-by-step explanation:

A Chi-square test is used to test the test of independence between rows and columns, contingency tables. It is a test related to frequencies. The observed frequency is a given statistical frequency known as the actual frequency,  the expected frequency is known as the theoretical frequency is derived from the study by using the sum total of the row and total in the column divided by their corresponding sample size.

yes. we do proportions in probabilities.