What is not so good about Tom finding opinions in this way?

The main disadvantage of opportunity/convenience sampling is that the sample is **unlikely to be representative** of the target population, and is therefore likely to be **biased**. For example: - **Location bias:** People at Manchester Piccadilly station do not represent the views of people in other cities or rural areas. - **Time bias:** Surveying on a Saturday afternoon means Tom is more likely to sample shoppers and people on leisure trips. He will miss weekday commuters, who might have very different opinions on a new train line. Because the sample is not representative, the findings cannot be reliably generalised to the wider population.