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2.4.4 Mean and variance of the binomial (A-level only)

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Question 12

Long-term telemetry data from an autonomous drone fleet shows that 15% of flight missions result in a high-wind sensor alert. In a random selection of 50 flight missions, let HHH denote the number of missions that triggered a high-wind alert.

a.

Write down a suitable distribution to model HHH.

[1]
b.

State one assumption necessary for this model to be valid.

[1]
c.

The probability that fewer than kkk missions result in a high-wind alert is less than 0.10.

Find the largest possible value of kkk.

[3]
d.

A larger random sample of 200 missions is analyzed.

The probability that at least mmm of these missions result in a high-wind alert is 0.901, correct to 3 decimal places.

Using a suitable approximation, find the value of mmm.

[5]
e.

The fleet undergoes a software optimization to better handle wind conditions. Subsequently, a random sample of 25 missions is taken and none of them (0) result in a high-wind sensor alert.

Test, at the 5% level of significance, whether there is evidence that the proportion of missions resulting in high-wind alerts has decreased. State your hypotheses clearly.

[5]

2.4.4 Mean and variance of the binomial (A-level only) Questions

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