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2.4 Probability Distributions

2.4 Probability Distributions

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Question 79

An electronics engineer measures the resistance, rrr ohms, of a specific component. The measured resistance, XXX ohms, is normally distributed with mean rrr ohms and standard deviation 0.80.80.8 ohms.

a.

Find the probability that XXX is within 1.01.01.0 ohm of rrr.

[2]
b.

The same component is measured 25 times and the results are recorded.

Find the probability that the sample mean of these 25 results, Xˉ\bar{X}Xˉ, is within 0.40.40.4 ohms of rrr.

[3]
c.

Given that the mean of these 25 measurements is 120.4120.4120.4 ohms, find a 95%95\%95% confidence interval for rrr.

[3]
Markscheme

2.4 Probability Distributions Questions

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

390 exam-style questions on OCR (MEI) A Level Maths 2.4 Probability Distributions, covering 2.4.1 Recognise binomial situations, 2.4.2 Probability of success p, 2.4.3 Calculate binomial probabilities, 2.4.4 Mean of the binomial distribution, 2.4.5 Expected frequencies for binomial, 2.4.6 Probability functions and discrete random variables, 2.4.7 Numerical probabilities for a simple distribution, 2.4.8 Normal distribution as a model (A-level only), 2.4.9 Shape of the Normal curve (A-level only), 2.4.10 Linear transformation and standardising (A-level only), 2.4.11 Symmetry and inflection of Normal curve (A-level only), 2.4.12 Calculate probabilities from a Normal distribution (A-level only), 2.4.13 Model with probability distributions, and 2.4 Probability Distributions. Each one has a worked solution and a mark scheme showing where the marks go.

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