20% of the people who say Yes drink at least three cups each day.
(a) Complete the frequency tree. [4 marks]
(b) What fraction of the 500 people drink at least three cups of coffee each day?
Give your answer in its simplest form. [2 marks]
Mark scheme (a)
Answer
Mark
Comments
450 in Drink coffee Yes
B1
50 in Drink coffee No
B1ft
ft 500 \(-\) their 450
90 in At least three cups Yes
B1ft
ft their 450 \(\div\) 5
360 in At least three cups No
B1ft
ft their 450 \(-\) their 90
Additional guidance
for 90 ft, their 450 ÷ 5 must be truncated or rounded up to the nearest whole number
for 360 ft, their 450 \(-\) their 90 must give a positive integer
Accept unambiguous values elsewhere but diagram values take precedence
Correct relative frequencies seen, withhold first B1 that would have been awarded. eg \(\dfrac{400}{500}, \dfrac{100}{500}, \dfrac{80}{400}, \dfrac{320}{400}\) eg \(\dfrac{400}{500}, \dfrac{100}{500}, \dfrac{80}{500}, \dfrac{320}{500}\)
B0 B0ft B1ft B1ft B0 B0ft B0ft B0ft
Do not accept probabilities eg \(\dfrac{9}{10}, \dfrac{1}{10}, \dfrac{4}{5}, \dfrac{1}{5}\) eg 0.9, 0.1, 0.8, 0.2
