## 1.11 Summary

In this chapter,
we have learnt about writing and understanding **research questions**.
Research questions (RQs) are always about an
**outcome** (O) in some **population**.
Some RQs have a **comparison** or **connection** (C),
and some also have an **intervention** (I).
RQs may be **estimation**-type RQs or **decision**-type RQs.

The outcome numerically summarises the
population or subsets of the population
(so is usually worded in terms of percentages, averages, etc.),
but the data comes from **individuals** in the population by
measuring, observing or assessing the **response** (or dependent) variable.
Similarly,
the data concerning the comparison or connection comes from
measuring or observing the **explanatory** (or independent) variables.

The *who* or *what* that observations are made from are called the
**units of observation**.
The smallest independent units
(that is, units with very little in common)
are called the **units of analysis**.

The following short video may help explain some of these concepts: