# [R] 4 questions regarding hypothesis testing, survey package, ts on samples, plotting

From: eugen pircalabelu <eugen_pircalabelu_at_yahoo.com>
Date: Tue, 18 Dec 2007 23:39:55 -0800 (PST)

Good morning!

I have 4 questions which trouble me:

1. I want to test the hypothesis that the 2 proportions (the mean of a binomial) which come from 2 different samples are equal. I want to use the following function z= (p1-p2)/ sqrt((p1(1-p1)/n1)+(p2(1-p2)/n2)) which is one of the standard formulas for this case. Is there such a function in R?
```p1=the proportion from the first sample
n1=the first sample size
p1=the proportion from the second sample
n2=the second sample size

```

2. How can i find the median of a variable in survey package? a<-c(1:10)
b<-sample(1:20, 10, replace=T)
b1<-sample(0:1, 10, replace=T)
c<-data.frame(a,b, b1)
library(survey)
design<-svydesign(id=~1, data=c)
svymean(~b, design)

svymean gives me the mean, but what function gives me the svymedian, and what function gives me the svyproportion for b1? I want to know the median for a metric variable and the proportion for a binomial variable ?

3. Could time series analysis (arima/arma) be applied on data that are obtained from a sample?. Eg: Say I have data from the same sample in 40 moments. Could I use arima/arma on the series? Or must i have data for the whole population like data from the Statistical Office on investment, inflation, demographics and so on?

4. I want to modify the scale of my axes within a plot but i really could not find this option. I think there is such an option, but i can not find it.  x<-rnorm(100, 100, 3)
x<-ts(x, frequency=12)
acf(x)
plot(x)
On the above example, i want to a scale like this 95,96,97,98,....104,105 (on y) and 1,2,3,4,...7,8 (on x).

Thank you very much and have a great day!

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