Foundation June 2025 Paper 3 Q11

OCRFoundationCurrent spec5 marksBasic Probability

11 A student has a three-sided spinner with sides labelled A, B and C.
They spin the spinner a number of times and record the results.

The student works out the correct relative frequencies for the spinner landing on sides A and B.
The relative frequencies are shown on this scale.

(a) Write down the relative frequency that the spinner landed on side A. [1]

(b)

(i) The student then works out the relative frequency that the spinner landed on side C is 0.4.

Explain, using a calculation, why the relative frequencies show that the student has made a mistake. [2]

(ii) On the scale above, mark with an arrow (↑) the correct relative frequency that the spinner landed on side C. [1]

The probability that the spinner will land on side B on my next spin is 0.1.

What assumption is the student making? [1]

Answer	Marks	Part marks and guidance
0.6 or 60% or \(\dfrac{6}{10}\)	1		Accept any equivalent fraction Do not accept in words or ratio

Mark scheme (b)

Answer	Marks	Part marks and guidance
(i) 1 0.1 + their 0.6 + 0.4 or 2 1 – (0.1 + their 0.6) oe or 3 0.6 + 0.4 = 1	B1		May be fractions or percentages Case 1 or 2: An answer does not need to be seen/correct to award first B1
and A valid comment implying not equal to 1 or 0.4 matching the calculation used	B1	Dep on relevant calculation with correct answer seen	Case 1 or 2: an answer must be seen and correct to award comment Example comments 1 The total should be 1 2 It should be 0.3 (not 0.4) 3 Nothing left for B See appendix
(ii) Arrow drawn at 0.3 cao	1		No FT Mark intention

Question 11(b)(i)

Assumption	Mark	Reason
0.1 + 0.6 = 0.7 which means it’s 0.3 He didn’t add 0.1	B0B0	Calculation is correct but incomplete B0 and final comment does not need to be considered following B0
1 + 6 + 4 adds up to 1.1 not 1	B0B0	The calculation is incorrect B0 and so the comment does not score
0.4 + 0.1 + 0.6 = 11.1 and frequencies have to add to 1	B1B0	B1 for the calculation (answer does not need to be correct for first B1) but B0 for comment as answer does need to be correct to reward this