Question 1
2 marksThe box plot shows information about the annual salaries of the 600 employees of a company.
Work out an estimate for the number of employees who earn more than £28 000.
Work out an estimate for the number of employees who earn between £22 000 and £28 000.
Model answer
£28 000 is the median, so half of the employees earn more: \(\dfrac{1}{2} \times 600 = 300\)
£22 000 is the lower quartile, so a quarter of the employees earn between £22 000 and £28 000: \(\dfrac{1}{4} \times 600 = 150\)
Explanation
The quartiles and the median split a population into four equal parts. Above the median is half of the population, and between the lower quartile and the median is a quarter. The scale is in thousands of pounds.
Mark scheme
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1 mark
B1 for 300
£28 000 is the median, so half of 600; correct answer with no working scores full marks
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1 mark
B1 for 150
from the lower quartile to the median is a quarter of 600