You conduct a well-designed study involving a random sample (n = 84). Age is measured in years. Your analysis shows that in this sample, age is normally distributed and representative of the population. The youngest subjects are 15 (n = 2), one subject is 16, and the oldest subject is 46 years old; the mean age is 29.4 years, and there is a standard deviation of 3 years.

If age is measured as 15–20 years, 25–35 years, and 35 years, what level of measurement is this variable?