Math Is Fun Forum
  Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

You are not logged in.

#1 2013-12-09 04:31:33

extjsjquery
Member
Registered: 2013-12-09
Posts: 4

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 ?

Offline

#2 2013-12-09 04:42:17

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,482

Re: odds ratio problem

Hi;

Are you doing something like this?

http://www.youtube.com/watch?v=ITi0SxmQTO8

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 agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

Offline

#3 2013-12-09 15:39:08

extjsjquery
Member
Registered: 2013-12-09
Posts: 4

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?

Offline

#4 2013-12-09 21:49:58

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,482

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 agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

Offline

Board footer

Powered by FluxBB