Displaying 20 results from an estimated 3000 matches similar to: "Problems with normality req. for ANOVA"
2004 Sep 07
1
Multiple comparisons in a non parametric case
Dear all,
I am conducting a full factorial analysis. I have one factor consisting
in algorithms, which I consider my treatments, and another factor made
of the problems I want to solve. For each problem I obtain a response
variable which is stochastic. I replicate the measure of this response
value 10 times.
When I apply ANOVA the assumptions do not hold, hence I must rely on non
parametric
2012 Mar 28
2
Test Normality
Good Night
I made different test to check normality and multinormality in my dataset,
but I don´t know which test is better.
To verify univariate normality I checked: shapiro.test, cvm.test, ad.test,
lillie.test, sf.test or jaque.bera.test and
To verify multivariate normal distribution I use mardia, mvShapiro.Test,
mvsf, mshapiro.test, mvnorm.e.
I have a dataset with almost 1000 data and 9
2011 Jun 23
3
trying to import xls or xlsx files
library(xlsReadWrite)
mydata<-read.xls("file path", header=TRUE)
however if I change xls to csv it works just fine. Any ideas what I'm doing
wrong? I have have also using the package gdata with the exact same error.
Below is the error that pops up.
Error in findPerl(verbose = verbose) :
perl executable not found. Use perl= argument to specify the correct path.
Error in
2012 Jul 20
6
Speeding up a loop
General problem: I have 20 projects that can be invested in and I need to
decide which combinations meet a certain set of standards. The total
possible combinations comes out to 2^20. However I know for a fact that the
number of projects must be greater than 5 and less than 13. So far the the
code below is the best I can come up with for iteratively creating a set to
check against my set of
2008 Feb 07
2
How to calculate normality of the residuals from a test in R?
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2012 Oct 12
3
Autofilling a large matrix in R
I wish to create a matrix of all possible percentages with two decimal place
percision. I then want each row to sum to 100%. I started with the code
below with the intent to then subset the data based on the row sum. This
works great for 2 or 3 columns, but if I try 4 or more columns the number of
rows become to large. I would like to find a way to break it down into some
kind of for loop, so
2006 Dec 19
4
nonparametric significance test for one sample
Hello, Gurus:
I tried to test if the sample mean of a dataset is zero.
The data has 1500 numbers with a lot of zeros and some small
positive numbers. The data range on [0,1] but the distribution is unknown.
It is zero inflated anyway.
I tried to use the Wilcoxon Signed Ranks test. But I read from this website
that it does assume the population pdf is symmetric.
2011 Jun 06
2
qplot fill and colour not working as expected
I am just learning to use qplot and can't get the fill/colour to work. Below
is the R code for a scatter plot and bar graph.
library(ggplot2)
x<-c(1,2,3,4,5,6,7)
y<-c(1,2,3,2,5,6,3)
qplot(x,y, main="Scatter Plot Test", xlab="X Label Test", ylab="Y Label
Test", colour="blue")z<-c("van", "van", "van",
2016 Apr 04
4
Fligner-Killeen test on binary data
Hello,
I investigate survival until the following year (0,1) and I wish to test if
the variance in survival for two or more groups are significantly different
from each other.
I read that the Fligner-Killeen test is a non-parametric test which is very
robust against departures from normality but is it correct (valuable
technique for publication) to use it on binary data?
In other
2012 Sep 07
4
Trying to learn how to write a function... can't define a variable??
I am just starting to experiment with writing a function and have run into
what seems like a limitation or more likely a lack of understanding on my
part.
Very Simple Example: I want to define a function that does 1+1=2.
z<-1
ADD<-function(x)
{
x<-x+1
}
ADD(z)
z
output for z is 1 not the expected 2.
Now if I were to do print(x+1) instead of x<-x+1 it does return 2, so the
2011 Jul 12
4
qplot and for loops
I have 4 columns and 56 rows of made up data that I want to plot as a series
of bar graphs. The idea is to create one bar graph for each of the 4 columns
using a for loop. I tried the following command in RStudio and when I type x
in the console I get just the 4th graph instead of all four graphs. I did
not define what x is before hand. I was not sure what it would be. Any
suggestions on how you
2012 Sep 26
3
Removing duplicates without a for loop
I have several thousand rows of shipment data imported into R as a data
frame, with two columns of particular interest, col 1 is the entry date, and
col 2 is the tracking number (colname is REQ.NR). Tracking numbers should be
unique but on occassion aren't because they get entered more than once. This
creates two or more rows of with the same tracking number but different
dates. I wrote a for
2016 Apr 04
0
Fligner-Killeen test on binary data
That's not an R question but a stats question, but I wouldn't do it. For one thing: The variance of binary data is a function of the mean, so the research question is dubious in the first place. Secondly, the test is based on ranking and comparing absolute differences from the group median, which for binary data is generally 0 or 1, so all absolute differences will be 1.... Put
2009 Nov 30
1
multiple comparisons with non homogeneus variances
This is a mixed question, between theory and practice.
I have a dataset with a continous variable grouped by a 33 levels
factor. After having log-tranformed my original data I can assume the
normality of my data but I have two strong departures from the basic
assumptions for anova and t tests: *unbalanced data* (some groups
contain ten samples, others hundreds) and *non homogenity of
variances*
2004 Oct 15
8
Testing for normality of residuals in a regression model
Hi all,
Is it possible to have a test value for assessing the normality of
residuals from a linear regression model, instead of simply relying on
qqplots?
I've tried to use fitdistr to try and fit the residuals with a normal
distribution, but fitdsitr only returns the parameters of the
distribution and the standard errors, not the p-value. Am I missing
something?
Cheers,
Federico
2007 Aug 04
3
Normality tests
Hello All,
I am new to R, and I am writing to seek your advice on how best to use it to run
R's various normality tests in an automated way.
In a nutshell, my situation is as follows. I work in an investment bank, and my
team and I are concerned that the assumption we make in our models that the
returns of assets are normally distributed may not be justified for certain
asset classes. We are
2010 Jul 09
3
Non-parametric regression
I have two data sets, each a vector of 1000 numbers, each vector
representing a distribution (i.e. 1000 numbers each of which
representing a frequency at one point on a scale between 1 and 1000).
For similfication, here an short version with only 5 points.
a <- c(8,10,8,12,4)
b <- c(7,11,8,10,5)
Leaving the obvious discussion about causality aside fro a moment, I
would like to see how
2012 Jul 23
2
Bug in my code (finding nonzero min)
Can someone verify for me if the for loop below is really calculating the
nonzero min for each row of a matrix? I have a bug somewhere in the is
section of code. My first guess is how I am find the the nonzero min of each
row of my matrix. The overall idea is to make sure I am investing all of my
money, i.e. new.set is a set of indicator variables for each stock for a
particular portfolio, i.e.
2011 Jun 21
2
qplot/ggplot2 Questions
I took some data from an online poll about which R GUI people used most and I
am messing around with it to learn how to use qplot. Specifically I am
making a horizontal bar graph and I have two questions.
1. The categories are ordered in rather strange way at least to me. It is
not alphabetical or ascending/descending order of votes cast so i had to
manually state the order I wanted which is
2011 Apr 15
1
GLM and normality of predictors
Hi,
I have found quite a few posts on normality checking of response variables, but I am still in doubt about that. As it is easy to understand I'm not a statistician so be patient please.
I want to estimate the possible effects of some predictors on my response variable that is nº of males and nº of females (cbind(males,females)), so, it would be: