Sampling

Sample questions

Original practice questions written in the style of the exam.

1. Question 14 marks

   A college has 360 students in Year 12 and 240 students in Year 13. The principal wants a sample of 50 students to complete a survey.

   (a) Explain how a stratified sample of size 50 could be taken.

   (b) Give one advantage of stratified sampling over simple random sampling in this situation.

   Mark scheme

   • M1 Sample in proportion to the size of each year group (1)
   • A1 $\tfrac{360}{600} \times 50 = 30$ from Year 12 and $\tfrac{240}{600} \times 50 = 20$ from Year 13 (1)
   • B1 Number the students in each year group (separate lists) and use random numbers to select within each group (1)
   • B1 Advantage: both year groups are guaranteed to be represented in proportion, so the sample better reflects the population (1)