Easy Statistics Question. (1 Viewer)

[SoCal]

I have had a think about this for a while and it is obviously pretty easy because the book and lecture slides don't bother to really explain it but I can't seem to see where they get the answer from. I would ask my lecturer but I won't see him for a week and I really want to know.

Anyway, the sentence is:

The probability that z falls between -z(α/2) and +z(α/2) is equal to 1 - α. For example, when 1 - α = 0.95, we have z(α/2) = z(0.025) = 1.96.

I understand everything except for why z(0.025) = 1.96?

Thanks for any help.

Note: the stuff in brackets are supposed to be subscripts.

 

[acmilan]

I think, but am not 100% sure, that z is the normal distribution function?

If you look at this table (2nd page):

http://www.maths.usyd.edu.au/u/UG/JM/MATH1905/r/formulaNEW.pdf

It shows the normal distribution values. You'll find that 1 - 0.025 = 0.9750

You can find 0.9750, which occurs at z = 1.96 (go down the first column to 1.90 and across to the column with heading 0.06). Thus z(0.025) = 1.96.

This is only my guess, it may not be whats actually needed.

 

[SoCal]

I think, but am not 100% sure, that z is the normal distribution function?

If you look at this table (2nd page):

http://www.maths.usyd.edu.au/u/UG/JM/MATH1905/r/formulaNEW.pdf

It shows the normal distribution values. You'll find that 1 - 0.025 = 0.9750

You can find 0.9750, which occurs at z = 1.96 (go down the first column to 1.90 and across to the column with heading 0.06). Thus z(0.025) = 1.96.

This is only my guess, it may not be whats actually needed.

Yeah, thanks heaps dude this was exactly right. After I read this I went back and I must have missed this:

z(A) is defined as the z value for which the area to the right of z(A) under the standard normal curve is A.

After reading that I understood it straight away. Thanks again.

 

[clive]

I have to study that crap for my midsemester quiz on monday

 

[SoCal]

At least it is easy. I did all this stuff last year, I am just having trouble trying to remember it.

 

[ballerinabarbie]

oh the joys of statistics...

anyone else have to use "R"? (its a statistical computer package)

 

[nit]

yep, I got a test on stats tomorrow, and it's partly testing R commands.

 

[Adam]

Stats is evil. So glad I passed it and never have to do it again

Ditto

52% and loving it!

 

[ballerinabarbie]

i have to do stat 200 in third year... although apparently its easier than stat 100...

and the joys of R... we have to do our assigments in R - but apparently our end of semester exam (70% of our mark) doesn't have a lot to do with R