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# S2 Help watch

1. Im cant seem to understand an example from the S2 revision book.

For those of you who have the book handy its chapter 3, page 26. Example 1 a and b

Q: the random varibale Z in continous unifrom random varibale on the interval (-4, 6).
Find
a) P(X < -2.5)
b) P(|X| < 1.3)

a) = 1.5 x 1/10= 0.5
b) = 2 x 1.3 x 1/10 = 0.26

i only understand how they got the 1/10 but no idea how they got the 1.5 or (in b) 2 x 1.3

any help is appreciated
thanks
2. Think of it as a number line (or a bar chart).
You need all the values less than -2.5, but the limit is -4. So that's 1.5 units you can go to the left for part a, and of course, multiply by the 1/10 for the area.

For part b, you need |X|<1.3
This means, -1.3 < X < 1.3

By drawing a number line, you can easily see that this covers 2.6 (=1.3*2) units. And then multiply by 1/10

Get it?
3. thanks, now i understand, i dont know why i got so confused!

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