In designing an experiment involving a treatment applied to

In designing an experiment involving a treatment applied to 4 test subjects, researchers plan to use a simple random sample of 4 subjects selected from a pool of 31 available subjects. (Recall that with a simple random sample, all samples of the same size have the same chance of being selected.) Answer the question below.

What is the probability of each simple random sample in this case?

Solution

There are 31C4 = 31465 ways to choose 4 subjects out of 31.

Thus, the probability of each simple random sample is

P(each simple random sample) = 1/31465 = 0.0000317813 [ANSWER]