Probability in Context
Reading and interpreting probability in workplace and everyday situations, including complements, independent events and two-way tables.
11 questions, free, marked as you go with a worked explanation on every one.
What this covers
- probability basics
- math30 3 probability in context
The questions
- A batch of 200 parts contains 12 that are defective. If one part is picked at random, what is the probability that it is defective? Give your answer as a percent.
- For that same batch of 200 parts with 12 defective, what is the probability that a randomly chosen part is NOT defective, as a percent?
- A machine produces a sound part 95% of the time, and each part is independent of the others. What is the probability that two parts in a row are both sound? Give your answer as a percent, rounded to two decimal places.
- A weather forecast gives the odds against rain as 3 : 2. What is the probability that it rains?
- A quality inspector checks 500 items and finds that 35 need rework. Based on this rate, how many items in a shipment of 4 000 would be expected to need rework?
- A survey of 300 workers records that 180 drive to work and 45 of those drivers also carpool. What is the probability that a randomly chosen worker both drives and carpools, as a percent?
- A fair six-sided die is rolled once. What is the probability of rolling a number greater than 4? Give your answer as a percent, rounded to one decimal place.
- A machine has failed on 2 of the last 100 shifts. A supervisor concludes that it is 'due to fail' because it has run without fault for the past 40 shifts. What is wrong with this reasoning?
- A survey finds that 18 out of 60 students surveyed prefer online classes. Based on this rate, how many students in a school of 900 would be expected to prefer online classes?
- A gambler loses five coin flips in a row and says 'the next flip is due to be heads.' What is wrong with this reasoning?
- A factory's defect rate is 3%. In a batch of 2500 items, how many would be expected to be defective?