Business Degree Certification Practice Test

When selecting two rolls of film without replacement, what is the probability of first selecting a defective roll and then another defective roll?

1. 1/4, or 0.25

2. 1/120, or about 0.0083

3. 1/15, or about 0.07

4. 1/2, or 0.50

The correct answer is: 1/15, or about 0.07

To determine the probability of selecting two defective rolls of film without replacement, you first need to know the total number of rolls of film and how many of them are defective. While the specific numbers are not provided, we can consider the general formula for calculating the probability in this scenario. The probability of selecting the first defective roll depends on the number of defective rolls available at the start and the total number of rolls. After selecting the first defective roll, there is now one less defective roll and one less total roll available for selection. Therefore, the probability of picking a second defective roll is then calculated based on these new totals. For instance, if there are 3 defective rolls out of a total of 6 rolls, the probability of selecting the first defective roll would be 3 out of 6. After selecting one defective roll, there would be 2 defective rolls left out of a total of 5 remaining rolls, resulting in a second probability of 2 out of 5 for the second selection. When you multiply these probabilities together, you find the overall probability of selecting two defective rolls consecutively without replacement. Thus, the answer indicates that the probability of selecting a defective roll followed by another defective roll, when properly calculated based on the total defective