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2.4.8 Normal distribution as a model (A-level only)

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Question 4

An oceanographic research station utilizes two distinct models of deep-sea power probes, Alpha and Beta, for underwater data collection. The battery life, XXX hours, of a Model Alpha probe is normally distributed such that X∼N(120,25)X \sim N(120, 25)X∼N(120,25). The battery life, YYY hours, of a Model Beta probe is normally distributed such that Y∼N(128,16)Y \sim N(128, 16)Y∼N(128,16). The battery lives of the probes are independent.

a.

Determine the probability that a Model Alpha probe, selected at random, outlasts a randomly selected Model Beta probe.

[4]
b.

An engineer deploys 3 Model Alpha probes and 1 Model Beta probe.

Calculate the probability that the sum of the battery lives of the 3 Model Alpha probes is greater than 2.5 times the battery life of the Model Beta probe.

[5]
c.

A composite metric SSS is defined as S=k1X+k2YS = k_1 X + k_2 YS=k1​X+k2​Y, where k1k_1k1​ and k2k_2k2​ are real constants. The engineer requires the mean of SSS to be exactly 3000 while ensuring the variance of SSS is minimized.

Determine the specific values of k1k_1k1​ and k2k_2k2​ that satisfy these requirements.

[4]

2.4.8 Normal distribution as a model (A-level only) Questions

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