When you plan a statistical study or explore data from someone else’s work, ask yourself the following questions

All the above and even more

Explanation

In practice, any set of data is accompanied by background information that helps us understand the data. When you plan a statistical study or explore data from someone else’s work, ask yourself the following questions:

1. Why? What purpose do the data have? Do we hope to answer some specific questions? Do we want to draw conclusions about individuals other than those for whom we actually have data?
2. Who? What individuals do the data describe? How many individuals appear in the data?
3. What? How many variables do the data contain? What are the exact definitions of these variables? Some variables have units. Weights, for example, might be recorded in pounds, in thousands of pounds, or in kilograms. For these kinds of variables, you need to know the unit of measurement.