<prompt> In random sampling chance of being picked up isSame and knownNot same and not knownSame and not knownNot same but known  <response>: Ans. is a Same known a Most samples used in biomedical research are probability samples, samples in which the researcher can specify the probability of each population element being includedThere are four basic kinds of probability samples:Simple random samplesStratified random samplesCluster samplesSystematic samplesSimple random sample is the simplest probability samples, it is a sample drawn so that every element in the population has an equal probability of being includedThus reading these above quoted lines, make it clear that the probability of being included ie chance of being picked up is same and the researcher can specify it ie the probability in known. 