Final answer:
The Chi-square test for independence is used to determine if there is a significant relationship between two or more categorical variables and to test for differences between two proportions.
Step-by-step explanation:
The instrument used to determine if there is a relationship between 2 or more categorical variables and to test whether the difference between two proportions is statistically significant is known as the test of independence. This is commonly done through a Chi-square test for independence, which utilizes a contingency table to compare the observed values to expected values if the two categories were independent. In cases where we want to compare two population proportions from independent samples, we use a test of two population proportions, which can be conducted using tools like the 2-PropZTest function on a calculator to calculate the p-value and determine the statistical significance.