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Qualitative data are 'categorical' (or binary) data, and as such are often not expressed numerically. These types of data can be classified as '''nominal''' and '''ordinal''':
Qualitative data are 'categorical' (or binary) data, and as such are often not expressed numerically. These types of data can be classified as '''nominal''' and '''ordinal''':
===Nominal===
===Nominal===
Nominal data include binary ('yes/no') and categorical data types, and are characterised by lacking any order between the different categories. As such, examples of nominal data are disease status (positive/negative), sex (male/female), breed and coat colour. As there is no numerical meaning to the data, nominal data are usually summarised with percentages or proportions.
Nominal data differ from all other data types described here by lacking any order between the different categories, and can be described further as either binary ('yes/no') or categorical in nature. Examples of binary data are disease status (positive/negative), sex (male/female) and presence/absence of a factor of interest; whereas examples of categorical data are breed, coat colour, location and feed type. As there is no numerical meaning to the categories themselves, nominal data are best summarised using percentages or proportions.
===Ordinal===
===Ordinal===
Ordinal data
Ordinal data are inherently categorical in nature, but have an intrinsic order to them. Examples of ordinal data are lameness score, level of agreement with a statement (Likert items), categorised weight and categorised lactation number. As can be seen in the last two examples here, ordinal data can be created through manipulation of quantitative data. It should be noted that even if numbers are used to describe these categories, these numbers do not necessarily follow the same scale (for example, the difference between a lameness score of 5 and 3 is not necessarily the same as the difference between scores of 4 and 2). As for nominal data, ordinal data are commonly described in terms of percentages or proportions, although the median may also be used as a '''measure of central tendency'''.
==Quantitative data==
==Quantitative data==