Annan has designed a new logo for a sportswear company. A survey of a large number of customers found that 42% of customers rated the logo as good.
- (i)A random sample of 10 customers is chosen. Find the probability that fewer than 8 of them rate the logo as good.[3]
- (ii)On another occasion, a random sample of n customers of the company is chosen. Find the smallest value of n for which the probability that at least one person rates the logo as good is greater than 0.995.[3]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2019). The mark or mark type is shown in brackets.
- [M1] Binomial term of form 10Ca pᵃ(1-p)ᵇ 0<p< 1 any p, 0 ≤ a,b ≤ 10
- [A1] Correct unsimplified expression
- [A1] 0.983
- [M1] Equation or inequality involving 0.58ⁿ or 0.42ⁿ and 0.995 or 0.005
- [M1] Attempt to solve using logs or Trial and Error. May be implied by their answer (rounded or truncated)
- [A1] CAO n=10
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