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2.4.13 Model with probability distributions

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Question 45

The continuous random variable TTT represents the deviation, in micrometres, of a high-precision digital caliper reading. The distribution of TTT is a continuous uniform distribution over the interval [0,2.5][0, 2.5][0,2.5].

a.

Determine P(T<1.0)P(T < 1.0)P(T<1.0).

[1]
b.

State the value of E(T)E(T)E(T).

[1]
c.

Calculate Var(T)Var(T)Var(T).

[2]
d.

A random sample of 20 readings taken by this caliper is recorded.

Find the probability that fewer than 9 of these readings show a deviation of more than 1.0 μm\mu \text{m}μm.

[3]
e.

For a different model of caliper, the deviation X μmX \, \mu \text{m}Xμm is represented by the cumulative distribution function F(x)F(x)F(x) defined by:

F(x)={0x<00.8x−0.16x20≤x≤2.51x>2.5 F(x) = \begin{cases} 0 & x < 0 \\ 0.8x - 0.16x^2 & 0 \le x \le 2.5 \\ 1 & x > 2.5 \end{cases} F(x)=⎩⎨⎧​00.8x−0.16x21​x<00≤x≤2.5x>2.5​

Using this model, find the value of P(X>1.0)P(X > 1.0)P(X>1.0).

[2]
f.

A large batch of 200 readings is collected from this different caliper.

Using a suitable approximation, find the probability that at least 80 of these readings show a deviation of more than 1.0 μm\mu \text{m}μm.

[4]

2.4.13 Model with probability distributions Questions

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