Question

Sampling. What kind of sample? At a party, there are 30 students over age 21 and 20 students under age 21. You choose at random six of those over 21 and separately choose at random four of those under 21 to interview about attitudes toward alcohol. A) Have you given every student at the party the same chance to be interviewed: what is that chance? B) Is this a simple random sample or another kind of sample that you are aware of?

Answer 1

A) No every student at party does not have same chance to be interviewed. Chances of choosing older student = 6/30 = 0.2 and chance of younger student selected = 4/20 = 0.2

Each student has 20% chance of being chosen but the only possible sample are with 6 older and 4 younger, not every set of 10 random students have same chance. Thus it is not simple random sample.

B) A simple random sample is sample where each participant has equal chance of being chosen. This is an example of stratified sample