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The Normal Distribution

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Question 71

The operational flight time, DDD minutes, of a specialized surveillance drone on a single battery charge is modelled by a normal distribution with mean μ\muμ and standard deviation σ\sigmaσ. Given that μ=45\mu = 45μ=45 and σ=2.5\sigma = 2.5σ=2.5, use standardisation to:

a.

(i) show that P(D<41.5)=0.0808P(D < 41.5) = 0.0808P(D<41.5)=0.0808 to four decimal places. (ii) find the value of d0d_0d0​ such that P(D<d0)=0.0150P(D < d_0) = 0.0150P(D<d0​)=0.0150

[5]
b.

A fleet manager randomly selects 5 drones from the production line.

Calculate the probability that every one of the 5 drones has a flight time exceeding 41.5 minutes.

[2]
c.

A software update is applied to the drones such that the flight time, DDD minutes, now has a mean μ=48\mu = 48μ=48 and a new standard deviation σ\sigmaσ.

Given that P(D<d)=0.0548P(D < d) = 0.0548P(D<d)=0.0548 and P(D>1.5d−21)=0.0082P(D > 1.5d - 21) = 0.0082P(D>1.5d−21)=0.0082,

determine the value of ddd and the value of σ\sigmaσ.

[5]

The Normal Distribution Questions

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