Question 17

Classify and describe the different types of data, including two examples of each.

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College Answer

Any reasonable classification was awarded marks. Standard textbooks well describe this topic,  often in their opening chapter. Broadly, qualitative (defined by some characteristic) vs and quantitative (measured on some numerical scale) data exists. These can also be described as categorical or numerical with subdivisions including ordinal, interval and ratio scales. Numerical data may be described as discrete or continuous. Appropriate examples and descriptions of each were required. For example:

Categorical data -when each individual can only belong to one of a number of distinct categories of the variable.

1. Nominal – categories not ordered but simply have a name e.g. blood group (A,B, AB, O) and marital status (married, single, widowed)
2. Ordinal – categories are ordered in some way e.g. disease staging (advanced, moderate, mild) or degree of pain (severe, moderate, mild, none)

Numerical data:

When the variable takes some numerical value
1. Discrete – when the variable can only take certain whole numerical values e.g. the 
number of visits to GP in last year, or the number of episodes of illness.

2. Continuous – when there is no limitation on the values that the variable can take e.g.weight or height.

Understanding types of data allows appropriate description and comparison with parametric or non-parametric statistics and better answers highlighted this.


In order to offer a "reasonable" classification, one need to refer to Myles and Gin where (at least in my 2000 edition) "Data Types" is the title of Chapter 1. This is an answer that benefits from a tabulated format

Types of Data and Examples
Data type Characteristics Examples
Qualitative Described by a characterstic or category

Marital status

Quantitative Described best by a number


Categorical There is a limited range of possible (qualitative) values


Numerical The variable is expressed as a number

Blood pressure

Nominal The range of possible categories is not ordered

Blood group

Ordinal The range of possible categories is ordered


Discrete Possible categories are restricted to a range

(i.e. dead or alive)

Continuous Possible range of values is on a continuum

Shades of colour

To be a "better answer", this table would have to be followed by some statement regarding the utility of such classification. In short,  if your measurement scale is nominal or ordinal then you use non-parametric statistics, whereas if you are using interval or ratio scales you can use parametric statistical tests.  Parametric tests assume that sample data have been taken from a normally distributed population. 


Lecture on types of data; by Keith G. Calkins

Richards, Derek. "Types of data." Evidence-based dentistry 8.2 (2007): 57-58.