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2.4 Statistical Distributions

2.4 Statistical Distributions

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Question 93

The probability that an attempted login fails is 0.04, independently of every other attempt. A sample of n n\,n login attempts is taken.

The probability that the sample contains at least one failed login is greater than 0.85.

a.

Show that 0.96n<0.150.96^n < 0.150.96n<0.15.

[2]
b.

Find the smallest possible value of nnn.

[2]
c.

State one assumption needed for the binomial model to be appropriate here.

[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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