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Solutions to the exercises

Exercise 1
a
b

The expected value is 80 16 = 5 .

Exercise 2
a

If the side facing up is white, and Bert bets on the other side being red, then only one of the three cards would make him win. His chance is therefore 1 3 .

b

P(3 bets) = ( 1 3 ) 3 + ( 2 3 ) 3 = 9 27 = 1 3 .

c

This cannot happen (after three bets a new series starts and they get new cookies), so the probability is 0.

Exercise 3
a

P ( T < 8 . 5 | μ = 9 . 2  and  σ = 0 . 6 ) = 0 . 12167
You would expect 0 . 12167 90 = 10 . 95 , or 11 years.

b

P ( T > 10 . 3 | μ = 9 . 2  and  σ = 0 . 6 ) = 0 . 033376 for a century, which is about 3 years per century.

Exercise 4

4 52 36 51 35 50 34 49 4 + 4 52 4 51 36 50 35 49 12 + 4 52 3 52 36 50 35 49 6 + 4 52 4 51 3 50 36 49 12 0 . 1570

Exercise 5
a

1 - 5 10 4 9 3 8 2 7 1 6 0 . 9960

b

1 - P ( V = 5 | n = 5 and p = 0 . 50 ) = 0 . 96875

Exercise 6
a

P ( V < 0 . 25 | μ = 0 . 27  and  σ = 0 . 01 ) 0 . 0228

b

P ( A 2 | n = 24  and  p = 0 . 0228 ) 0 . 9832

c

P ( V < 0 . 25 | μ = m  and  σ = 0 . 01 ) 0 . 01 gives you ( 0 . 25 - m ) 0.01 - 2 . 326 and therefore m = μ 0 . 273 .
On average, the machine needs to dispense 0.273 litres into each bottle.

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