A Bloomberg Businessweek North American subscriber study collected data from a sample of 2861 subscribers. Fifty-nine percent of the respondents indic

a.
A population is the collection of all possible events for an experiment.
In this case, the study is based on the subscribers of Bloomberg Businessweek North American.
Thus, all of the subscribers of Bloomberg Businessweek North American is the population of the study.
b.
In statistics, according to measurement, data can be categorized in two types, such as quantitative data and categorical data.
Quantitative variable can take numerical values, whereas categorical variable is used to identify the characteristics of a variable as categories. Moreover, mathematical operations cannot be performed on categorical data, but can be performed on quantitative data.
The annual income can be measured in terms of dollar. Moreover, mathematical operations can be done on the annual income. Hence, annual income is quantitative variable.
c.
The ownership of an American Express card just defines the people, whether hey are using the American Express card or not. Moreover, any mathematical operation cannot be done on this.
Hence, the ownership of an American Express card is a categorical variable.