20 of the 32 adults who did the test passed. 6 of the children who did the test failed.
(a) Use this information to complete the frequency tree.(3)
One of these people is picked at random.
(b) Find the probability that this person is an adult who failed the test. (2)
Mark scheme (a)
Answer
Mark
Mark scheme
Frequency diagram
See end of m/s
C3
for a fully correct frequency diagram
(C2
for at least 5 correct values in the frequency diagram)
(C1
for at least 3 correct values in the frequency diagram)
Additional guidance
If probabilities used instead of frequencies then maximum of C2 can be awarded
Mark scheme (b)
Answer
Mark
Mark scheme
\(\dfrac{12}{72}\)
M1
for \(\dfrac{a}{72}\) where \(0 \lt a \lt 72\) and \(a\) is an integer or \(\dfrac{12}{b}\) where \(b \gt 12\) and \(b\) is an integer or 12 : 72 or ft their values for 72 and/or 12 from (a)
A1
for \(\dfrac{12}{72}\) oe or ft (a)
Additional guidance
Accept equivalent decimal or percentage forms of probability Ignore errors in cancelling of their \(\dfrac{12}{72}\)
