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At ABC College the withdrawal rate from an elementary physics course is 30% every term, so 70% of students finish the course. If X counts students who withdraw from a randomly selected class, what should be defined as a 'success' for this binomial setup?
AA student who finishes the entire course
BA student who withdraws from the course
CA student who enrolls in the course at all
DA randomly selected physics course itself
Answer & Solution
Correct answer: B. A student who withdraws from the course
1. The random variable X is defined as the number of students who withdraw.
2. In a binomial setup, 'success' must match what X is counting.
3. Since X counts withdrawals, success is defined as an individual who withdrew, with p = 0.30 and q = 0.70.
4. Option A swaps success and failure, and options C and D describe events the problem never asks about.
_Source: OpenStax Introductory Statistics (CC BY 4.0), Ch 4 "Discrete Random Variables", section 4.3 Binomial Distribution_
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