[R] Data Censoring and Normality Tests
Liaw, Andy
andy_liaw at merck.com
Wed Nov 10 00:47:00 CET 2004
I stand corrected! Hope Bert doesn't mind me CC'ing the list.
Andy
> From: Berton Gunter
>
> No Andy, they're (left) censored alright: their values are
> known to be below
> 2.4, but not how far below. Truncated data "arise when
> observations are
> actually observed only when they take on values in a
> particular range (above
> 2.4, say). For observations outside that range, their EXISTENCE is not
> known." -- Meeker and Escobar, "Statistical Methods for
> Reliability Data."
>
> Cheers,
> Bert
>
>
>
> > -----Original Message-----
> > From: r-help-bounces at stat.math.ethz.ch
> > [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Liaw, Andy
> > Sent: Tuesday, November 09, 2004 3:12 PM
> > To: 'Kenneth Frost'; r-help at stat.math.ethz.ch
> > Subject: RE: [R] Data Censoring and Normality Tests
> >
> > I don't know much about censored data, but what you described
> > doesn't sound
> > like censored data, but rather truncated data.
> >
> > I think normality tests are over-(ab)used, and would suggest
> > inspection of
> > normal QQ plots instead (as you already do). For formal
> > tests, you might be
> > able to cook up something that test for truncated normality.
> >
> > Cheers,
> > Andy
> >
> > > From: Kenneth Frost
> > >
> > > Hello,
> > >
> > > I would like to know if there is a function in R that
> will test for
> > > normality and handle censored data sets. Currently, I
> > evaluate each
> > > censored data set by the extent to which a normal scores plot
> > > approximate a straight line. For complete data sets I use
> > > shapiro.test().
> > >
> > > Below is an example of a censored data set.
> > >
> > > data1<-c(0.00, 0.00, 0.00, 5.86, 5.17, 8.17, 5.12, 4.92,
> > > 7.08, 5.73,
> > > 5.44, 6.61, 6.34, 6.23, 5.97, 5.86, 5.15, 7.98, 6.72, 5.15,
> > > 3.58, 6.86,
> > > 6.12, 4.58, 6.07, 5.38, 5.21, 3.78)
> > >
> > > The zero values occur because I cannot detect a pathogen
> > with a value
> > > below 2.4. Using shapiro.test(), it seems that the data are
> > > different
> > > from a normal distribution. However, the normal scores
> > plot suggest
> > > otherwise.
> > >
> > > Using R version 1.9.1
> > >
> > > Thanks in advance.
> > >
> > > Ken
> > > ________________________________________________________
> > > Kenneth E. Frost
> > > Research Assistant
> > > University of Wisconsin - Madison
> > > Dept. of Plant Pathology
> > > 1630 Linden Dr.
> > > Madison, WI 53706
> > > kef at plantpath.wisc.edu
> > >
> > > ______________________________________________
> > > R-help at stat.math.ethz.ch mailing list
> > > https://stat.ethz.ch/mailman/listinfo/r-help
> > > PLEASE do read the posting guide!
> > > http://www.R-project.org/posting-guide.html
> > >
> > >
> >
> > ______________________________________________
> > R-help at stat.math.ethz.ch mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide!
> > http://www.R-project.org/posting-guide.html
> >
>
More information about the R-help
mailing list