Question

A bloomberg businessweek north american subscriber study collected data from a sample of 2861 subscribers. fifty-nine percent of the respondents indicated an annual income of $75,000 or more, and 50% reported having an american express credit card.
a. what is the population of interest in this study?
b. is annual income a categorical or quantitative variable?
c. is ownership of an american express card a categorical or quantitative variable?
d. does this study involve cross-sectional or time series data?
e. describe any statistical inferences bloomberg businessweek might make on the basis of the survey.

Answer 1

a. The population of this study consists of all subscribers to Bloomberg Newsweek in North America.

b. Quantitative variables are those that can be measured numerically. Annual income is a quantitative variable since it can be expressed in numbers.  

c. Categorical variables are those that can’t be quantified. They can only take on a fixed number of values. In this case, the question ‘do you own an American express credit card’ can take on only two values – Yes or No. So, the ownership of an American Express credit card is a categorical variable.

d. The data above gives two different values that describe the same population at the same time, it involves cross-sectional data.

Time-series data refers to data that is collected at equally spaced time intervals. For e.g. production of wheat in each year for the last 10 years, the amount of rainfall received over each of the last five years etc.

Cross-sectional data refers to data from many (similar)individual groups at one given point in time. For e.g. Prices of different varieties of corn on a particular day.

e. On the basis of the survey, Bloomberg Newsweek might infer that at least some of its subscribers with an income of $75,000 or more have an American Express credit card.