A middle school contains sixth, seventh, and eighth graders. Each grade level contains approximately the same number of students. The principal wants to find the answer to a survey question affecting each student in the school. He asks a sample group “What time do you get up in the morning?” Which of these characteristics define the best sample?
Answer
A
one student chosen at random from each grade level
B
an equal number of students chosen at random from each grade level
C
all students arriving on one bus
D
the first 10 students from each grade level to arrive at school in the morning
Explanation
The sample should represent students from all three grade levels, and choosing students at random helps avoid selection bias. Since each grade has approximately the same number of students, an equal number chosen randomly from each grade gives a balanced, representative sample. One student per grade is too small, while students on one bus or the first to arrive may share habits that make them unrepresentative.
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