Problem
42. Two students were chosen at random from each first period class and asked to complete a survey about their sleep habits. What sampling method was used?
Solution
Step 1 ：Two students were chosen at random from each first period class and asked to complete a survey about their sleep habits. The sampling method used is Stratified Sampling.
Step 2 ：Final Answer: The sampling method used is \(\boxed{\text{Stratified Sampling}}\)
