On Fri, 3 Apr 2009, Paul Jones wrote:
Hi,
I'm trying to get standard errors for some of the variables in my data frame.
One of the questions on my survey is whether faculty coordinate across
curriculum to include Arts Education as subject matter. All the responses are
coded in zeros and ones obviously. For some of the other variables I have a 2
for those that responded with "Don't Know".
I'm getting NA for mean and standard deviations from svymean. Am I doing
something wrong of can the survey package not handle this type of data?
Are you sure you don't have any NA values in the data? If you do, the
na.rm=TRUE option to svymean() will fix your problem. If you don't,
something mysterious is happening. You could try svytable(~Curriculum,
survey), which will give a tabulation and might show up what is strange
about your data.
As a separate issue, you might want to look at svyciprop() if some of your
proportions are close to 0 or 1, to get better confidence intervals.
Here's my code.
Nothing obviously wrong with it.
-thomas
survey <- svydesign(id=~1, data=General, strata=~Grade.Level)
Warning message:
In svydesign.default(id = ~1, data = General, strata = ~Grade.Level) :
No weights or probabilities supplied, assuming equal probability
summary(survey)
Stratified Independent Sampling design (with replacement)
svydesign(id = ~1, data = General, strata = ~Grade.Level)
Probabilities:
Min. 1st Qu. Median Mean 3rd Qu. Max.
1 1 1 1 1 1
Stratum Sizes:
Elementary High Middle
obs 312 236 156
design.PSU 312 236 156
actual.PSU 312 236 156
Data variables:
[1] "Grade.Level" "Curriculum" [3]
"Field.Trips" "Residencies" [5] "PTA.Support"
"Community.Open.Performances"
[7] "Visual.Arts.Attendance" "Literary.Arts.Attendance" [9]
"Arts.Organization.Membership" "Arts.Essential"
> svymean(~Curriculum, survey)
mean SE
Curriculum NA NA
???
PJ
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Thomas Lumley Assoc. Professor, Biostatistics
tlum...@u.washington.edu University of Washington, Seattle
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