Final answer:
The correct response is option b. variables, which represent characteristics or measurements that can change and are not fixed, like IQ score, age, weight, GPA, and income.
Step-by-step explanation:
The correct answer is option b. variables. IQ score, age, weight, grade point average, and income are all examples of characteristics or measurements that can vary from one person to another in a given population. These are called variables because the data they represent can change and do not have a fixed value. Specifically, variables like these are typically referred to as quantitative variables since they represent data that can be measured and expressed numerically.
For instance, age and weight are both numerical variables because they represent measurements with specific numeric values. Similarly, grade point average (GPA) and income are also considered numerical variables as they too have numeric representations. This contrasts with categorical variables, which describe data that can be sorted into categories but not measured numerically, such as a person's favorite type of music or their political affiliation.