Displaying 20 results from an estimated 4000 matches similar to: "shapiro wilk normality test"
2008 Sep 17
3
t-test between percentages
Hi all,
though i know this is a simple question, i really hope someone could.
I am just trying to compare percents respectively the difference in
percents by a simple test. t.test usually compares means and is
working like it is supposed to be. Now i wonder how i can use a test
in R to test for significant difference between two percentages.
2001 Jul 02
2
Shapiro-Wilk test
Hi,
does the shapiro wilk test in R-1.3.0 work correctly? Maybe it does, but can
anybody tell me why the following sample doesn't give "W = 1" and
"p-value = 1":
R> x<-1:9/10;x
[1] 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
R> shapiro.test(qnorm(x))
Shapiro-Wilk normality test
data: qnorm(x)
W = 0.9925, p-value = 0.9986
I can't imagine a sample being
2008 Nov 21
1
question about shapiro.test()
Hi all!
I tried to perform Shapiro-Wilk test for my sample of 243 values.
> Us
[1] -10.4 -13.1 -12.2 38.1 -18.8 -13.3 -11.7 29.3 49.7 6.8 12.7 16.3
[13] 5.8 -0.7 -29.4 4.1 38.8 -1.4 8.8 15.6 32.9 -5.3 19.1 35.8
[25] 4.0 -1.5 0.6 -4.2 -10.0 -4.0 1.1 48.9 -21.0 -5.3 5.8 -10.8
[37] 21.9 8.2 -3.2 -3.9 -2.3 12.6 -4.7 -8.0 11.8 27.4 -9.5 -20.8
[49]
2000 Sep 25
1
Interpretation of Shapiro-Wilk
Can anybody tell me the exact meaning of the $statistic and $p.value
calculated by shapiro.test? Unfortunately it is not covered in my few
text books, and I cannot find the explanation in the R documentatiom or
on-line.
If I have a test statistic, T, which is Normally distributed with mean=m
and sd=s under the null hypothesis, then I can convert T to a p-value
(one-sided) using:
p <- pnorm(T,
2013 Apr 05
2
How to perform a grouped shapiro wilk test on dataframe
Hello,
I was wandering if it is possible to perform on a dataframe called 'all' a
shapiro wilk normality test for COUNTS by variable Group
ACTIVITY? Could it be done using plyer? I saw an eg that applies to an
array but not to a dataframe:
lapply(split(dataset1$Height,dataset1$Group),shapiro.test)
Any thoughts would be much appreciated.
My dataframe is in shape:
dat ACTIVIT
2012 Apr 04
1
Shapiro-Wilk cpoefficients: 2 Qs
Greetings!
I want to have the coefficients that R uses in shapiro.test()
for the Shapiro-Wilk test for a prticular sample size, i.e.
the a[i] in
W = Sum(a[i]*x[i])/(Sum(x[i] - mean(x))^2)
(where the x[i] are sorted). Two questions:
Q1:
Is there a readymade R function from which I can extract these?
Q2:
I was wondering if I might be able to modify the code for the
function shapiro.test() so
2004 Nov 17
1
R: log-normal distribution and shapiro test
Hi,
from what you're writing:
"The logaritmic transformation
"shapiro.test(log10(y))" says: W=0.9773, p-value=
2.512e-05." it seems the log-values are not
distributed normally and so original data are not
distributed like a log-normal: the p-value is
extremally small!
Other tests for normality are available in package:
nortest
compare the log-transformation of your ecdf
2005 Nov 09
1
Problems with Shapiro Wilk's test of normality.
Hi,
I am trying to create a table with information from Shapiro Wilk's
test of normality.
However, it fails due to lack of sample size, it says, but the way I
see it, this is not a problem.
(See the table of sample sizes (almost) at the bottom).
Applying a different function using a similar ftable call is not a
problem (See the bottom table).
This is R 2.1.0 on Linux (Gentoo).
/Fredrik
1999 Nov 04
1
shapiro wilk
I'm pretty new to R and are trying to do some reliable normality
testing... but, can't find the Shapiro Wilk test in R Does some
experienced user have such a function that will be wanting to share with
me? Or there is maybe some other way to get hte Shapiro Wilk test
done... I'll appreciate any hint on this,
Thanks
--
***********************
Horacio Samaniego
Dep. Ecologia
P.
2010 Apr 09
6
How to run Shapiro-Wilk test for each grouped variable?
I want to run Shapiro-Wilk test for each variable in my dataset, each
grouped by variable groupFactor.
I have these working commands:
> data.n<-names(data) # put names into a vector called data.n
> by(eval(parse(text=(paste("data",data.n[3],sep="$")))), data$factor, shapiro.test) #run shapiro.test
but I must to change the variable number manualy. How to automate
2010 Feb 18
1
Shapiro-Wilk test problem
Hi everybody,
Does anyone know what problem may be with this test.
I am applying 5 different normality tests and use p-values for them, but for
some reason S-W gives me NA, while sample size is 100.
Any ideas?
Thanks a lot!
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2009 May 04
2
normality test for large a large dataset ?
Hello,
Do you know a R implemented normality test like the shapiro test but more suitable for large data set ?
Thanks,
_________________________________________________________________
Découvrez toutes les possibilités de communication avec vos proches
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2005 Nov 17
1
(no subject)
Hi there,
I am trying to perform different normality tests in R. I have no problem
when I use Shapiro.test( ). However, when I try to use any normality
tests from the Nortest package, I kept getting this error " Error in
read.table(source, header = T, fill = T) :
'file' must be a character string or connection". I have no idea
why because there was no problem with
2007 Mar 01
7
count the # of appearances...
Hi there,
is there a possibility to count the number of appearances of an
element in a vector ?
i mean of any given element.. deliver all elements which are exactly
xtimes in this vector ?
thx in advance !!
2008 Jul 14
0
"Reasonable doubt" - was "Re: shapiro wilk normality test"
>>> Ted Harding <Ted.Harding at manchester.ac.uk> 14/07/2008 00:16 >>>
>said:
>What constitutes "reasonable doubt" can become a very interesting
>question, but there are some crimes for which it has a definite
>statistical interpretation
Warning for potential courtgoers: "reasonable doubt" NEVER has a direct
statistical interpretation in a
2006 Jun 13
1
Cramer-von Mises normality test
Hi, this is my first help request so please bear with me.
I've been running some normality tests using the nortest package. For
some of my datasets the Cramer-von Mises normality test generates an
extremely high probability (e.g., 1.637e+31) and indicates normality
when the other tests do not. Is there something I'm misunderstanding
or potentially a bug in the code?
Below are the
2010 Apr 28
7
operator problem within function
Dear all,
i have a problem with processing dataframes within a function using the "$".
Here´s my code:
recode_items = function(dataframe,number,medium=2){
# this works
q<-paste("columna",number,sep="")
# this does not work, particularly because "dataframe" is not processed
# dataframe should be: givenframe$columnagivennumber
2008 Jan 13
1
Shapiro-Wilk
What is the formula used in Shapiro-Wilk Statistic?
Thanks
Eduardo (S?o Paulo/ Brazil)
2007 Feb 27
5
Multiple conditional without if
Dear all,
i am stuck with a syntax problem.
i have a matrix which has about 500 rows and 6 columns.
now i want to kick some data out.
i want create a new matrix which is basically the old one except for all
entries which have a 4 in the 5 column AND a 1 in the 6th column.
i tried the following but couldn´t get a new matrix, just some wierd
errors:
2011 Jan 24
2
normality and equal variance testing
I currently have a program that automates 2-way ANOVA on a series of endpoints,
but before the ANOVA is carried out I want the code to test the assumptions of
normality and equal variance and report along with each anova result in the
output file. How can I do this?
I have pasted below the code that I currently use.
library(car)
numFiles = x #