ABSTRACT
Chapter 15 looked at some of the graphical and numerical techniques that you can use to describe your data, for both exploratory and presentational purposes. However, unless the population of interest is small enough for you to have gathered data from every case, descriptive techniques alone will not answer your research questions. You cannot expect a sample to precisely refl ect the population in every respect however carefully you have chosen it to be as representative as possible. Moreover, if you took repeated samples from the same population, the samples would vary one from another. This is known as sample variation. You may fi nd an interesting pattern or effect in your particular sample, but how do you know if this result truly refl ects what is happening in the wider population? Is it a ‘real’ result, or simply sample variation?
