[R] prop.trend.test issue

[Michael Dewey]

At 13:46 03/12/2006, Ethan Johnsons wrote:
>I don't find any other test avail for this?
>Am I missing something?

I do not want to seem unhelpful but the only response that springs to 
mind is a knowledge of statistics.

I hope people's lives are not at stake with the results of your analysis

>thx
>
>ej
>
>On 12/3/06, Michael Dewey <info at aghmed.fsnet.co.uk> wrote:
>>At 05:55 03/12/2006, Ethan Johnsons wrote:
>> >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.
>>
>>If you want to test means why did you think a test for proportions
>>was a good idea?
>>
>>
>> >>  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
>> >
>> >
>>
>>Michael Dewey
>>http://www.aghmed.fsnet.co.uk
>>
>
>
>
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>01/12/2006 13:12

Michael Dewey
http://www.aghmed.fsnet.co.uk