October 2021 Paper 2 Q5

OCR MEICurrent spec3 marksBinomial Distribution

5 It is known that 40% of people in Britain carry a certain gene.

A random sample of 32 people is collected.

(a) Calculate the probability that exactly 12 people carry the gene. [1]

(b) Calculate the probability that at least 8 people carry the gene, giving your answer correct to 3 decimal places. [2]

Scheme	Marks	AO
0.14, 0.139 or awrt 0.1385 isw BC	B1	1.1
	[1]

Scheme	Marks	AO
\(\mathrm{P}(X \leqslant 7) = 0.0248(2\ldots)\) soi or 0.9751 to 0.9752 seen	M1	1.1
0.975 cao	A1	1.1
	[2]