Which of the following statements on data types are correct?

(i) If 100 managers are surveyed and asked to state their age, the responses they give are real numbers and are called nominal data.

(ii) One most important aspect of ordinal data is the order of the values. As a result, the only permissible calculations are those involving a ranking process.

(iii) The four most popular sources of statistical data are: (1) data collected from surveys, (2) data collected from experimental studies, (3) data collected from observational studies, and (4) published data.