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

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Question 24

A commercial coffee machine dispenses espresso shots and steamed milk for lattes. The volume of an espresso shot, EEE ml, follows the distribution N(30.2,1.22)N(30.2, 1.2^2)N(30.2,1.22). The volume of a portion of steamed milk, MMM ml, follows the distribution N(220.5,4.52)N(220.5, 4.5^2)N(220.5,4.52). A barista prepares a "Large Latte" using a random sample of 3 espresso shots and 2 portions of steamed milk.

a.

Find the probability that the total volume of these 5 components exceeds 540 ml.

[4]
b.

A customer orders two portions of steamed milk to be served separately.

Determine the probability that the volumes of these two portions differ by more than 5 ml.

[3]
c.

To calibrate the machine, a technician takes a random sample of n+1n+1n+1 espresso shots with volumes E1,E2,E3,…,En+1E_1, E_2, E_3, \dots, E_{n+1}E1​,E2​,E3​,…,En+1​. The random variable TTT is defined as

T=nE1−∑r=2n+1Er T = n E_1 - \sum_{r=2}^{n+1} E_r T=nE1​−r=2∑n+1​Er​

Given that P(T>30)=0.0533P(T > 30) = 0.0533P(T>30)=0.0533 to 4 decimal places,

find the value of nnn.

[5]

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

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