prop.trend.test issue
I have the clinical study data. Year 0 Year 3 Retinol (nmol/L) N Mean +-sd Mean +-sd Vitamin A group 73 1.89+-0.36 2.06+-0.53 Trace group 57 1.83+-0.31 1.78+-0.30 where N is the number of male for the clinical study. I want to test if the mean serum retinol has increased over 3 years among subjects in the vitamin A group.
1.89+0.36
[1] 2.25
1.89-0.36
[1] 1.53
2.06+0.53
[1] 2.59
2.06-0.53
[1] 1.53
prop.trend.test(c(2.25, 1.53),c( 2.59, 1.53))
Chi-squared Test for Trend in Proportions
data: c(2.25, 1.53) out of c(2.59, 1.53) ,
using scores: 1 2
X-squared = 0.2189, df = 1, p-value = 0.6399
The issue I am seeing that N of Vitamin A group = 73 seems not reflected.
This leads me to think that I can't implement the test based on the
data just presented.
Nor a two-tailed test is possible.
2-sample test for equality of proportions with continuity correction
data: c(2.25, 1.53) out of c(2.59, 1.53)
X-squared = 0, df = 1, p-value = 1
alternative hypothesis: two.sided
95 percent confidence interval:
-0.6738203 0.4112720
sample estimates:
prop 1 prop 2
0.8687259 1.0000000
Warning message:
Chi-squared approximation may be incorrect in: prop.test(c(2.25,
1.53), c(2.59, 1.53))
Any ideas, please?
thx
ej