ABSTRACT
Generally our research questions refer to whole populations of interest, such as all teachers, all young children, all secondary school pupils. However, after having specified a population (step 1), it is often impossible to collect data for the whole population of interest. Instead, a sample from the population is selected (step 2). A wise researcher should give careful thought to the kind of statistical inference(s) required to address the research question(s) at the planning and design stage, that is before data is collected.
