A2 June 2025 Q1

EdexcelCurrent spec3 marksDecision Analysis

1. Ravi can choose one of three options, A, B or C, when playing a game. The profit, in pounds, associated with each outcome, and the corresponding probabilities, are shown in the decision tree in Figure 1.

Figure 1: decision tree. Decision node with branches A, B and C. A leads to a chance node with outcomes 0.55: 370, 0.25: 250, 0.2: -75. B leads to a chance node with outcomes 0.75: 245, 0.25: 195. C leads to a chance node with outcomes 0.45: 390, 0.4: 325, 0.15: -280 — Figure 1

Calculate the optimal EMV to determine Ravi’s best course of action. You must make your working clear. (3)

Mark scheme

Scheme	Marks	AO
EMV for A is \(0.55(370) + 0.25(250) + 0.2(-75) = 251\) EMV for B is \(0.75(245) + 0.25(195) = 232.5\) EMV for C is \(0.45(390) + 0.4(325) + 0.15(-280) = 263.5\)	M1 A1	3.4 1.1b
The optimal EMV is £263.50, which makes option C the best choice (using the EMV criterion)	A1	2.2a
	(3)
	(3 marks)

Notes

Note: Working (or values) may be seen on the diagram as well as on the lined page. If both seen, the answers on the lined page take precedent. Completion of the diagram is not necessary.

M1: Correct method for calculation EMV for either A, B or C

A1: Correct values of EMV for A, B and C

A1: Correct deduction of optimal EMV (dependent on all three correct EMVs) C must be clearly identified in some way, either stated or indicated with e.g. an arrow. If all working is shown on the diagram with 263.50 written in the decision node, they must still indicate C in some way.