Praxis Core Academic Skills for Educators: Mathematics (5733)Statistics and ProbabilityEasy
A quality control engineer is testing a new production line. Out of 200 items produced, 10 are found to be defective. If this rate continues, what is the probability that the next item produced will NOT be defective?
- A0.10
- B0.95
- C0.05
- D0.90
Show answer & explanationAnswer & explanation
Correct answer: B. 0.95
The number of defective items is 10 out of 200. So, the number of non-defective items is 200 - 10 = 190. The probability of an item not being defective is 190/200 = 0.95.
Why the other options are wrong
- A. Incorrect calculation.
- C. This is the probability of an item being defective (10/200).
- D. Incorrect calculation.
Complementary Probability
The probability of an event not occurring is 1 minus the probability that it does occur.
- P(not A) = 1 - P(A).
- The sum of the probability of an event and its complement is always 1.
- Useful for calculating 'at least one' type problems.
Memory trick: What you want, or everything else.