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    • Thread Starter

    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).
    a) P(X < -2.5)
    b) P(|X| < 1.3)

    answers have been given as
    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

    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?
    • Thread Starter

    thanks, now i understand, i dont know why i got so confused!
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Updated: April 13, 2006
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