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# s2 - hypothesis tests watch

1. 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
2. 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
3. fantastic bobbob, you are a life saver! =)
4. ive done that question today, and i dont know either. i got confused aswel! exactly the same confusion!
sorry im not much help!!
5. i see!

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