4MA0 Higher June 2011 Paper 4 Q2

EdexcelHigherOld spec4 marksBasic Probability

2 John throws a biased coin 120 times.
It shows heads 90 times.

(a) John throws the coin once more.
Work out an estimate for the probability that the coin shows tails. (2)

Carly throws the same coin 200 times.

(b) Work out an estimate for the number of times the coin shows tails. (2)

Mark scheme (a)

Scheme	Marks
120 − 90 (=30)	M1
30/120 oe	A1
	(2)

Notes

M1: or 1 − 90/120

Apart from questions 5b, 8, 15d, 20b, 21b, 23, 24b (where the mark scheme states otherwise) the correct answer, unless clearly obtained by an incorrect method, should be taken to imply correct working.

Scheme	Marks
“30/120” × 200 oe	M1 ft
50	A1 ft
	(2)
	(Total 4 marks)