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

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Question 9

A specialist coffee machine dispenses espresso shots and steamed milk. The volume of an espresso shot, EEE ml, is normally distributed such that E∼N(35,2.52)E \sim N(35, 2.5^2)E∼N(35,2.52).

Four espresso shots are selected at random.

a.

Find the probability that their total volume exceeds 146.5 ml.

[3]
b.

The volume of a portion of steamed milk, MMM ml, is normally distributed such that M∼N(150,62)M \sim N(150, 6^2)M∼N(150,62).

Two espresso shots and three portions of milk are selected at random.

Find the probability that the total volume of these five components is less than 500 ml.

[4]
c.

A random sample of nnn portions of milk M1,M2,…,MnM_1, M_2, \dots, M_nM1​,M2​,…,Mn​ is taken. A new random variable VVV is defined by the espresso machine's calibration offset:

V=(n−1)M1−∑r=2nMr V = (n-1)M_1 - \sum_{r=2}^{n} M_r V=(n−1)M1​−r=2∑n​Mr​

Given that P(V>41.57)=0.0228P(V > 41.57) = 0.0228P(V>41.57)=0.0228 correct to 4 decimal places,

determine the value of nnn.

[5]

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

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