Basic Quantitative Research Methods for Urban Planners

by Reid Ewing

There are four scales of measurement. First, nominal scale categorizes cases with no numerical equivalent (e.g., male/female, introvert/extrovert, city/suburb). Second, ordinal measurement can rank-order the cases, but the distances between attributes have no meaning. For example, five-star hotels are supposed to be better than lower-ranked hotels in terms of accommodations and services. However, we do not know if the distance from 5-star to 4-star is the same as 4-star to 3-star. A better example for planners is the categorization of people as low income, medium income, or high income. Thirdly, in interval measurement, we can assume equal intervals between values. Typical examples include temperature and IQ. When we measure temperature (in Fahrenheit), the distance from 30 to 40 is the same as the distance from 70 to 80. Note, however, that in interval measurement, ratios don’t make any sense and there is no true zero (0 degree Celsius does not mean no temperature). Sprawl metrics developed by Ewing and Hamidi (2014) are measured in terms of standard deviations above and below the mean, but there is no true zero when it comes to compactness or sprawl. Lastly, ratio measurement always has a meaningful absolute zero, i.e., zero indicates the absence of variable measured. Weight, age, and frequency of behaviors are examples. It is called ratio scale because you can construct a meaningful fraction or ratio with its values: someone can weigh twice as much as another, or can wa...