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i was asked to do an assignment on examining the Body Mass index of students. I have to select at least 50 students from my school, and i was asked to describe how I ensure the randomness of the sample. Can anyone explain to me how can i ensure the randomness of my samples?

Guestttt
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Ideally you would put all the students in your school into a numbered list ($1, 2, ..., N$). Then, using a random number generator (or a list of random numbers), you would pick $50$ random numbers from $1$ to $N$, and use the corresponding students on the list for your sample.

paw88789
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  • Because my teacher knew that i wasnt doing that way. Can i say that i recorded 80 students' BMI from three classes and i use the number generator to select 50 from the 80???? – Guestttt Sep 18 '14 at 14:27
  • That would be a random sample of the $80$ students in the three classes, but not a random sample from the whole school. I guess ultimately it would be up to your teacher to decide if that was suitable. – paw88789 Sep 18 '14 at 14:29