A researcher wants to survey 500 secondary school students in a large city to find out their favourite type of movie. The researcher visits one large school and surveys the first 500 students they meet. Based on this method, what is the most likely source of bias?

1. Read the description of the sampling method. 2. Identify the population (secondary school students in a large city). 3. Identify the sample (the first 500 students from one specific school). 4. Compare the sample to the population. Does the sample represent the entire population? 5. The population includes students from all schools in the city, but the sample is from only one. This is a key difference. 6. Consider other aspects: "first 500 students" is a convenience sample, which is also a source of bias. However, the most significant issue is the lack of representation from other schools. 7. State the main source of bias.