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2.4 Statistical Distributions

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Question 98

An inspector takes a random sample of 20 items from a production line. The probability that any item is faulty is 0.08, independently of every other item. A sample is rejected if it contains 3 or more faulty items.

a.

Find the probability that a sample is rejected.

[2]
b.

The inspector takes 6 such samples, independently. Find the probability that exactly 2 of them are rejected.

[3]
c.

Find the expected number of rejected samples out of the 6.

[1]
Markscheme

2.4 Statistical Distributions Questions

  1. A Level
  2. /Maths
  3. /2.4 Statistical Distributions

390 exam-style questions on OCR A Level Maths 2.4 Statistical Distributions, covering 2.4.1 Discrete probability distributions, 2.4.2 Binomial distribution as a model, 2.4.3 Calculating binomial probabilities, 2.4.4 Mean and variance of the binomial (A-level only), 2.4.5 Normal distribution as a model (A-level only), 2.4.6 Probabilities using the normal distribution (A-level only), 2.4.7 Links to histograms, mean and standard deviation (A-level only), and 2.4.8 Selecting an appropriate distribution (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.

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