A university randomly chooses four lecture groups and surveys every student present in those groups about weekly study time.
Describe the sampling structure.
Give two reasons why the results may not represent all university students.
Suggest one refinement and explain how it addresses a stated weakness.
36 exam-style questions on OCR (MEI) A Level Maths 2.1 Sampling, covering 2.1.1 Population and sample, 2.1.2 Samples to make informal inferences, 2.1.3 Random sampling, 2.1.4 Variety of sampling techniques, 2.1.5 Select or evaluate sampling techniques, and 2.1 Sampling. Each one has a worked solution and a mark scheme showing where the marks go.