Handling Data 4
3 marks · NormalSunny records whether it rains on each of 12 days in July. Her results are:
| Day | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rain? | ✓ | ✗ | ✓ | ✗ | ✓ | ✗ | ✗ | ✓ | ✓ | ✗ | ✓ | ✓ |
Estimate the experimental probability that it rains on a randomly chosen day.
Estimate how many days in a 30-day month you would expect to have rain.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) 7/12 or 0.58
(b) 17 or 18
Common mistakes: Dividing by incorrect number of days; Incorrect multiplication for expected value
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Counts 7 rainy days out of 12.
A1 (a) · 1 mark · Probability given correctly as 7/12 or 0.58 to 2 decimal places.
A2 (b) · 1 mark · Correct expected number: 0.58 × 30 = 17.4 (accept 17 or 18). (follow-through)
Worked solution
Number of rainy days = 7
Expected number = 0.58 × 30 = 17.4 (either 17 or 18 days)