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The Normal Distribution

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Question 3

The random variable TTT represents the water temperature level (in ∘C^{\circ}\text{C}∘C) at a specific marine research site. The probability distribution for TTT is given in the following table:

ttt25810
P(T=t)P(T=t)P(T=t)0.20.30.30.2
a.

Show that E(T)=6.3E(T) = 6.3E(T)=6.3.

[2]
b.

Find Var(T)Var(T)Var(T).

[3]
c.

The random variable SSS represents the salinity index at the same site, recorded as a discrete index. The probability distribution for SSS is given in the following table:

sss368kkk
P(S=s)P(S=s)P(S=s)0.250.250.250.25

Name the probability distribution of SSS.

[1]
d.

Given that E(S)=E(T)E(S) = E(T)E(S)=E(T), find the value of kkk.

[2]
e.

A specific species of bioluminescent jellyfish is found at a depth DDD meters, where D∼N(μ,σ2)D \sim N(\mu, \sigma^2)D∼N(μ,σ2). In a simulation, two researchers, Alice and Bob, each generate values for the parameters of the distribution. They each obtain a value for TTT to use as μ\muμ and a value for SSS to use as σ\sigmaσ. The researcher whose parameters yield the higher probability P(D>7.0)P(D > 7.0)P(D>7.0) wins.

Alice obtained t=8t = 8t=8 and s=3s = 3s=3. Bob obtained s=6s = 6s=6. Find the probability that Bob wins.

[4]
f.

Determine the largest value of P(D>7.0)P(D > 7.0)P(D>7.0) achievable in this simulation.

[2]
g.

Find the probability of a researcher achieving this maximum value.

[1]

The Normal Distribution Questions

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