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    hi

    im just reviewing hypothesis tests in S2 and have a question regarding
    two tailed hypothesis tests...

    1) X~B(20, 0.25)

    Test at level of 10% significance.

    in the markscheme given...it seems they have taken a 5% left and right tail and then found the critical regions, etc.

    and from looking in the tables that is P (X<1) = 0.0243, and P(X<8) = 0.9591

    with a CR of X<1 and X>9

    2) X~B (25, 0.2)

    "Find the CR for a two tailed test...probability of rejection in either tail should be as close as possible to 2.5%."

    here the mark scheme states the tails are P(X<1) = 0.0274, and
    P(X>10) = 0.0173

    so im kinda confused, it seems they divided the 10% in Q1) by 2 to get 5% tails on each side, but in this question they havent done that

    if anyone could shed some light on this that'd be great
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    Simple.

    In the first question, it's asking you for a total 10% significence level, so that's 5% for each tail (as you have to split it into two - 5% for each side of the normal curve) so outside the critical region is 10% in total.

    In the second question, it's asking for each tail to be 2.5%, so that's 2.5% for each tail so outside the critical region is 5% in total.

    It's different ways to saying things. It's best to draw one of those funky graphs to help you visualise.

    Hope this helps
    • Thread Starter
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    fantastic bobbob, you are a life saver! =)
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    ive done that question today, and i dont know either. i got confused aswel! exactly the same confusion!
    sorry im not much help!!
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    i see!
 
 
 
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