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Finding Probabilities for Normal Distributions

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Question 4

The lifetime of Lumos LED bulbs, XXX units of hours, is normally distributed with mean 12,000 hours and standard deviation 800 hours.

ai.

Find P(X≠12000)P(X \neq 12000)P(X=12000).

[1]
aii.

Find P(11000<X<13500)P(11000 < X < 13500)P(11000<X<13500).

[3]
b.

Determine the lifetime exceeded by 80% of Lumos LED bulbs.

[3]
c.

A different brand, Glow, has its bulb lifetime, YYY hours, modelled by a normal distribution with mean 11,000 hours and standard deviation σ\sigmaσ. Given that 15% of randomly selected Glow bulbs last less than 9,500 hours, find the value of σ\sigmaσ, correct to three significant figures.

[3]

Finding Probabilities for Normal Distributions Questions

  1. A Level
  2. /Maths
  3. /Finding Probabilities for Normal Distributions

Practise Edexcel A Level Maths Finding Probabilities for Normal Distributions with exam-style questions for A Level Maths. 80 questions, matched to the Edexcel A Level Maths (9MA0) specification and written in Paper 1, Paper 2 and Paper 3 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.

Question bank