Florida Teacher Certification Examinations (FTCE) Subject Area Practice Test

What are the odds against getting the correct answer by pure guessing on a multiple-choice test with a 20% probability?

1. 3:1

2. 4:1

3. 5:1

4. 1:4

The correct answer is: 4:1

To determine the odds against getting the correct answer by pure guessing in a scenario where there is a 20% probability of selecting the correct answer, you first look at the probability of not selecting the correct answer. If there is a 20% chance of selecting the correct answer, this implies that there is an 80% chance (100% - 20%) of not selecting it. Odds against an event are represented as the ratio of the probabilities of the event not occurring to the event occurring. In this case, the odds against guessing correctly can be calculated by comparing the probability of guessing incorrectly (80%) with the probability of guessing correctly (20%). Thus, we have: Odds against = Probability of not getting it right : Probability of getting it right = 80% : 20% = 4 : 1 The correct response reflects this ratio, which shows that for every one time the correct answer might be guessed, it is expected that it will not be guessed four times. Understanding this helps in recognizing how multiple-choice options can be structured in relation to their probabilities.