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3.2 Finding Probabilities for Normal Distributions

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Question 4

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

ai.

Find $\neq 12000)$ .

[1]

aii.

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

[3]

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

[3]

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

[3]

Markscheme

3.2 Finding Probabilities for Normal Distributions Questions

A Level
Maths
3.2 Finding Probabilities for Normal Distributions

80 exam-style questions on Edexcel A Level Maths 3.2 Finding Probabilities for Normal Distributions. Each one has a worked solution and a mark scheme showing where the marks go.

3.2 Finding Probabilities for Normal Distributions

Question bank

3.2 Finding Probabilities for Normal Distributions

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52

Question 4

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

ai.

Find $\neq 12000)$ .

[1]

aii.

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

[3]

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

[3]

Markscheme

3.2 Finding Probabilities for Normal Distributions Questions

A Level
Maths
3.2 Finding Probabilities for Normal Distributions

80 exam-style questions on Edexcel A Level Maths 3.2 Finding Probabilities for Normal Distributions. Each one has a worked solution and a mark scheme showing where the marks go.