Question

what is the primary reason for using the chi - square analysis?
to calculate observed values
to determine the sample size
to measure cell division rates
to compare expected and observed values

Explanation:

Chi - square analysis is a statistical method. Its main purpose is to check if there is a significant difference between the expected frequencies and the observed frequencies in one or more categories. It is not for calculating observed values (they are input), determining sample size (other methods like power analysis are used), or measuring cell division rates (biological assays are for that).

Answer:

to compare expected and observed values