Data structure

Context is critically important, but the statistical methods that can be used on data depend mostly on the internal structure of the data.

Testing of grapes
Variety  Sugar content 
A
A
A
A
A
A
B
B
B
B
B
B
62
46
51
79
44
60
72
55
78
63
81
53
Bird weight
Sex Weight
Male
Male
Male
Male
Male
Male
Female
Female
Female
Female
Female
Female
62
46
51
79
44
60
72
55
78
63
81
53
Yield of wheat
Fertiliser? Yield
No fert
No fert
No fert
No fert
No fert
No fert
Fert
Fert
Fert
Fert
Fert
Fert
62
46
51
79
44
60
72
55
78
63
81
53

These three data sets have the same basic structure, so the same statistical methods can be applied to all of them.

Variables and 'individuals'

Most data sets have a fairly simple structure. One or more measurements ('variables') are recorded from each of a collection of 'individuals' (also called 'cases' or 'units'). The data can be presented in a data matrix.