> prop.test(c(271,433),c(6164113,5572041))
2-sample test for equality of proportions with continuity correction
data: c(271, 433) out of c(6164113, 5572041)
X-squared = 54.999, df = 1, p-value = 1.206e-13
alternative hypothesis: two.sided
95 percent confidence interval:
-4.291428e-05 -2.457623e-05
sample estimates:
prop 1 prop 2
4.396415e-05 7.770941e-05
At 06:36 AM 6/10/2010, Phender79 wrote:
Hi,
I'm totally new to R so I apologise for the basic request. I am looking at
the incidence of a disease over two time periods 1990-1995 and 2003-2008. I
have counts for each year, subdivided into three disease categories and by
males/females.
I understand that I need to analyse the data using poisson regression and
have managed to use the pois.daly function to get age-sex adjusted rates and
corresponding confidence intervals. However, I now want to know how get a p
value (I'm writing up a paper for a journal) to say that x number of cases
in the first cohort (1990-1995) is significantly lower than y number in the
later cohort (2003-2008). I also want to make sure that I've corrected for
overdispersion etc.
I'm totally stuck and can't think where to start with writing a script. So
basically my question is:
e.g. I have 271 cases of the disease between 1990-1995 (total population at
risk over six years = 6,164,113) and 433 cases between 2003-2008 (total
population at risk over sic year = 5,572,041) - is this significant and what
is the P value.
Any help much appreciated!
Cheers
P
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