ALEVELPAPERZ2025
Mark Scheme (Results)
Summer 2025
Pearson Edexcel GCE
In Mathematics (9MA0)
Paper 31 Statistics
, ALEVELPAPERZ2025
Question Scheme Marks AOs
1(a)(i) 4
[ Let p = probability of yellow from bag B] P(YY) = ×p M1 1.1b
12
4 × p =3 so p = 9 (Allow 0.5625 and condone 0.563)
12 A1 1.1b
16 16
(2)
1(a)(ii) B1 1.1b
B1ft 1.1b
(2)
1(b) e.g. P(RY) + P(Y) + P(GY) or 1 – P(RR) – P(GR) or P(…Y) + P(YR) M1 2.1
5 "9" 4 3 "9" 5 "7" 3 "7" "9" 1 "7"
× + + × or 1 − × + × or + × A1ft 1.1b
12 "16" 12 12 "16"
12 "16" 12 "16" "16" 3 "16"
136 17
= = = 0.7083 A1 1.1b
192 24
(3)
1(c) P (W ∩ X ) × "16"
3 "9"
[ P(W | X ) =] or 12
M1 1.1b
P( X ) "(b)"
27
= A1 1.1b
136
(2)
(9 marks)
Notes:
(a)(i) M1 for a suitable expression (in their p) for the probability both are yellow.
A1 for correct probability of yellow from B. Can be implied by values on tree diagram.
(a)(ii) B1 for a correct 1st column of tree diagram (probabilities from A)
B1ft (dep on M1 in (i)) for correct 2nd column of tree diagram (ft their 9
16 and 1 – 9
16 )
(b) for selection of all correct cases (including the 1 – if required). Don’t need P(… may be
M1
implied by correct probability products seen (ft their tree diagram)
A1ft for a correct complete probability expression (ft their tree diagram) or awrt 0.708
Must see product pairs (for ft) or implied by correct values e.g. 15 64 + 48 + 16 + 64
7 3 9
2 "7"
May see 1 − P (Y Y ) (M1) and 1 − × (A1ft)
3 "16"
A1 for an exact answer …fraction needn’t be simplified but decimal must have … 3
(c) M1 for a correct ratio of probabilities expression (in symbols) or ft their values seen
A1 for an exact answer NB an answer of awrt 0.199 (0.198529411…) implies M1
Acc If scored 2nd A0 in (b) for 0.708 (or better) then allow A1 in (c) for awrt 0.199
Mark Scheme (Results)
Summer 2025
Pearson Edexcel GCE
In Mathematics (9MA0)
Paper 31 Statistics
, ALEVELPAPERZ2025
Question Scheme Marks AOs
1(a)(i) 4
[ Let p = probability of yellow from bag B] P(YY) = ×p M1 1.1b
12
4 × p =3 so p = 9 (Allow 0.5625 and condone 0.563)
12 A1 1.1b
16 16
(2)
1(a)(ii) B1 1.1b
B1ft 1.1b
(2)
1(b) e.g. P(RY) + P(Y) + P(GY) or 1 – P(RR) – P(GR) or P(…Y) + P(YR) M1 2.1
5 "9" 4 3 "9" 5 "7" 3 "7" "9" 1 "7"
× + + × or 1 − × + × or + × A1ft 1.1b
12 "16" 12 12 "16"
12 "16" 12 "16" "16" 3 "16"
136 17
= = = 0.7083 A1 1.1b
192 24
(3)
1(c) P (W ∩ X ) × "16"
3 "9"
[ P(W | X ) =] or 12
M1 1.1b
P( X ) "(b)"
27
= A1 1.1b
136
(2)
(9 marks)
Notes:
(a)(i) M1 for a suitable expression (in their p) for the probability both are yellow.
A1 for correct probability of yellow from B. Can be implied by values on tree diagram.
(a)(ii) B1 for a correct 1st column of tree diagram (probabilities from A)
B1ft (dep on M1 in (i)) for correct 2nd column of tree diagram (ft their 9
16 and 1 – 9
16 )
(b) for selection of all correct cases (including the 1 – if required). Don’t need P(… may be
M1
implied by correct probability products seen (ft their tree diagram)
A1ft for a correct complete probability expression (ft their tree diagram) or awrt 0.708
Must see product pairs (for ft) or implied by correct values e.g. 15 64 + 48 + 16 + 64
7 3 9
2 "7"
May see 1 − P (Y Y ) (M1) and 1 − × (A1ft)
3 "16"
A1 for an exact answer …fraction needn’t be simplified but decimal must have … 3
(c) M1 for a correct ratio of probabilities expression (in symbols) or ft their values seen
A1 for an exact answer NB an answer of awrt 0.199 (0.198529411…) implies M1
Acc If scored 2nd A0 in (b) for 0.708 (or better) then allow A1 in (c) for awrt 0.199
