What are the odds against getting the correct answer by guessing on a multiple choice test with a 20% chance of a correct answer?

To determine the odds against getting the correct answer by guessing on a multiple-choice test with a 20% chance of selecting the correct answer, it's crucial to first understand the probability of getting it incorrect. If there is a 20% chance of answering correctly, then there is an 80% chance of answering incorrectly.

Odds against an event are expressed as the ratio of the probability of the event not happening to the probability of the event happening. In this case, the event 'getting the correct answer' happens 20% of the time and does not happen 80% of the time.

Calculating the odds against getting the correct answer involves taking the probability of not getting it right (80%) and comparing it to the probability of getting it right (20%). This gives us:

• Odds against = Probability of being wrong : Probability of being right

• Odds against = 80% : 20%

• This simplifies to 4 : 1.

Thus, the correct choice reflects that for every one time a student might guess the correct answer, there are four times when they would guess incorrectly, resulting in odds of 4:1 against guessing correctly.