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## #1 2013-12-10 03:31:33

extjsjquery
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### odds ratio problem

I input a,b,c,d  use odds ratio calculator

Cases with positive outcome
Number in 1st group:    a=25
Number in 2nd group:    b=15
Cases with negative outcome
Number in 1st group:    c=18
Number in 2nd outcome:    d=30

and calculate

Results
Odds ratio    2.8889
95 % CI    1.2184 to 6.8497
z statistic    2.408
P = 0.0160

I know odds ratio is Odds ratio = (a/c) / (b/d)
my question is
what z statistic    and p mean ?

## #2 2013-12-10 03:42:17

bobbym

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### Re: odds ratio problem

Hi;

Are you doing something like this?

I am getting an OR = 2.7777777777

Also I think you mean P rather than p.

Z scores are measures of standard deviation. P is a probability.

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #3 2013-12-10 14:39:08

extjsjquery
Novice

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### Re: odds ratio problem

Tks for your reply.  I input a wrong number that Number in 1st group:    a=26
not 25    if 25  ,2 .777  is  right.
like formula Odds ratio = (a/c) / (b/d) ,what is the formula for probability？

## #4 2013-12-10 20:49:58

bobbym

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### Re: odds ratio problem

Hi;

You can get a probability from the odds.

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.