The convenience sample often suffers from biases from a number of biases. This can be seen in both of our examples, whether the 10,000 students we were studying, or the employees at the large organisation. In both cases, a convenience sample can lead to the under-representation or over-representation of particular groups within the sample. If we take the large organisation: It may be that the organisation has multiple sites, with employee satisfaction varying considerably between these sites. By conducting the survey at the headquarters of the organisation, we may have missed the differences in employee satisfaction amongst non-office workers. We also do not know why some employees agreed to take part in the survey, whilst others did not. Was it because some employees were simply too busy? Did not trust the intentions of the survey? Did others take part out of kindness or because they had a particular grievance with the organisation? These types of bias are quite typical in convenience sampling.
As you conduct research, you are likely to realise that the topic that you have focused on is more complex than you realised when you first defined your research question. The research is still valid even though you are now aware of the greater size and complexity of the problem. A crucial skill of the researcher is to define clearly the boundaries of their research and to stick to them . You may need to refer to wider concerns; to a related field of literature; or to alternative methodology; but you must not be diverted into spending too much time investigating relevant, related, but distinctly separate fields.