The lifetime of Lumos LED bulbs, XXX units of hours, is normally distributed with mean 12,000 hours and standard deviation 800 hours.
Find P(X≠12000)P(X \neq 12000)P(X=12000).
Find P(11000<X<13500)P(11000 < X < 13500)P(11000<X<13500).
Determine the lifetime exceeded by 80% of Lumos LED bulbs.
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.
616 exam-style questions on Edexcel A Level Maths The Normal Distribution, covering 3.1 The Normal Distribution, 3.2 Finding Probabilities for Normal Distributions, 3.3 The Inverse Normal Distribution Function, 3.4 The Standard Normal Distribution, 3.5 Finding the mean and standard deviation, 3.6 Approximating a Binomial Distribution, and 3.7 Hypothesis Testing with the Normal Distribution. Each one has a worked solution and a mark scheme showing where the marks go.