Question

Standard Tests Standard tests, such as the SAT or ACT or MCAT, tend to make extensive use of multiple-choice questions because they are easy to grade using software. If one such multiple choice question has possible correct answers of a, b, c, d, e, what is the probability of a wrong answer if the answer is a random guess?

Short answer

The probability of choosing a wrong answer is 0.8.

Step-by-step solution

Given information

One of the standard tests has five choices for correct answers; a,b,c,d, and e.

Describe the probability of any event

Any event defined as E would have a probability described as follows:

$P\left(E\right)=\frac{\text{Number}\text{of}\text{favourable}\text{outcomes}}{\text{Total}\text{number}\text{of}\text{outcomes}}$

Let E be an event that the answer is wrong when guessed randomly.

Assume there is only one correct answer.

Thus, the number of outcomes supportive (wrong answers) of event E is 4.

The total number of outcomes that are possible is 5.

The probability of the wrong answer is computed as follows:

$$\begin{gathered} P\left(E\right)=\frac{4}{5} \\ =0.8 \end{gathered}$$

Therefore, the probability that the chosen answer is wrong is 0.8.