| Date | May 2012 | Marks available | 1 | Reference code | 12M.3sp.hl.TZ0.3 |
| Level | HL only | Paper | Paper 3 Statistics and probability | Time zone | TZ0 |
| Command term | Explain | Question number | 3 | Adapted from | N/A |
Question
Each week the management of a football club recorded the number of injuries suffered by their playing staff in that week. The results for a 52-week period were as follows:
Calculate the mean and variance of the number of injuries per week.
Explain why these values provide supporting evidence for using a Poisson distribution model.
Markscheme
mean = 2.06 A1
variance = 1.94 A1
[2 marks]
a Poisson distribution has the property that its mean and variance are the same R1
[1 mark]
Examiners report
Many candidates picked up good marks for this question, but lost marks because of inattention to detail. The mean of the data was usually given correctly, but sometimes the variance was wrong. It may seem a small point, but the correct hypotheses should not mention the value of the estimated mean. Some candidates did not notice that some columns needed to be combined.
Many candidates picked up good marks for this question, but lost marks because of inattention to detail. The mean of the data was usually given correctly, but sometimes the variance was wrong. It may seem a small point, but the correct hypotheses should not mention the value of the estimated mean. Some candidates did not notice that some columns needed to be combined.
