similar to: Item Analysis and Cronbach's Alpha (Code Attached)

Hi all, I am trying to teach myself to use and program R (How else do you do it? lol) Anyway, I wrote a piece of code to compute coefficent alpha for a scale. As I am neither a statistician nor a programmer, I wanted people's feedback. The code appears to work (Win 95 with R 1.0.1) and I have verified my result with SPSS and it was correct (much to my astonishment!). Nonetheless, I am

Dear All, I am a novice in R and am working on my thesis for master's in Epidemiology & Biostatistics. While calculating Cronbach's alpha for the SF-36 questionnaire, I got all 8 of them more than 1. Is it possible to get alpha more than 1. If yes, please help me understand it. I read about the negative alpha value on your web postings. It does not answer my question though. Thank you.

Hi list members Any easy way to get standardized cronbach's alpha for a scale, as in SPSS? Thanks Steve Powell proMENTE social research research | evaluation | training & consulting Kranj?evi?eva 35, 71000 Sarajevo mobile: +387 61 215 997 | office: +387 33 556 865 | fax: +387 33 556 866 Checked by AVG Free Edition. 17:44

hie 1...i'm trying to carryout a relibility testusing cronbach's alpha what fuctin do i use. 2.. this is more of a statistical question.if the alpha value for all the variables is negative what does it mean. and if the alpha value is negative for all tyha variables but is greater than 0.7 for some sections of the variables what does that mean thanks in advance

Dear all, I like the way the Rcmdr package computes reliability. E.g reliability(cov(d[,c("q1", "q2", "q3", "q4", "q5", "q6")], use="complete.obs")) will not only give me the alpha score, but also for each variable, alpha.score if deleted. However - when writing scripts it's very tiresome to load the whole Rcmdr GUI just

Dear Listers: I used cronbach{psy} to evaluate the internal consistency and some set of variables gave me alpha=-1.1003, while other, alpha=-0.2; alpha=0.89; and so on. I am interested in knowing how to interpret 1. negative value 2. negative value less than -1. I also want to re-mention my previous question about how to evaluate the consistency of a set of variables and about the total

Dear all, i need help about comparing 2 alpha cronbach. How to derive W statistic. Are alpha cronbach and Hoyt's method using ANOVA identical? Thank you for your help. Regards --------------------------------- Luggage? GPS? Comic books? [[alternative HTML version deleted]]

Erin Hodgess wrote: > Date: Mon, 05 Jun 2006 08:05:04 +0200 > From: Tom Backer Johnsen <backer at psych.uib.no> > User-Agent: Thunderbird 1.5.0.4 (Windows/20060516) > MIME-Version: 1.0 > To: r-help at stat.math.ethz.ch > References: <4481F48B.6090308 at imst.math.uni-magdeburg.de> > In-Reply-To: <4481F48B.6090308 at imst.math.uni-magdeburg.de> >

I spent a lot of time searching and came up empty handed on the following query. Is there an equivalent to rowSums that does product or cumulative product and avoids use of apply or looping? I found a rowProd in a package but it was a convenience function for apply. As part of a likelihood calculation called from optim, I?m computing products and cumulative products of rows of matrices with

Hi, I have a matrix and time series "xmat". I have no problem executing any matrix functions except t(xmat) which gives the following error message. My question if "xmat" is a matrix why I can not execute this matrix function?? converting the time series and matrix into a data frame solves the problem >dim(xmat) [1] 98 7 > t(xmat) Error in "tsp<-"(*tmp*,

dear all. Would someone be kind and willing to explain the code below for a person who has never used R? ( that is if one has enough time and inclination) It implements gillepsie's stochastic algorithm for Lotka Volterra model. What would help me tremendously is to see the breakdown of the line by line code into plain english. thanks for any insights or other comments. sean

Hi, I was wondering if there is a way, or function in R to find confounders. For istance, > a = sample( c(1:3), size=10,replace=T) > X1 = factor( c('A','B','C')[a] ) > X2 = factor( c('Aa','Bb','Cc')[a] ) > Xmat = data.frame(X1,X2,rnorm(10),rnorm(10)) > dimnames(Xmat)[[2]] = c('z1','z2','z3','y') Now,

I get different results from match.call(), according to whether a function is dispatched via S3 or S4. Specifically, when I use S4 dispatch in the following example, the match.call() result is of length 1 less than I expect. I need to add an extra comma to get the same results as in the S3 method. --------example setClass("foo",representation("matrix"))

R-users E-mail: r-help@r-project.org Hi! R-users. http://finzi.psych.upenn.edu/R/library/mvpart/html/xpred.rpart.html says: data(car.test.frame) fit <- rpart(Mileage ~ Weight, car.test.frame) xmat <- xpred.rpart(fit) xerr <- (xmat - car.test.frame$Mileage)^2 apply(xerr, 2, sum) # cross-validated error estimate # approx same result as rel. error from printcp(fit) apply(xerr, 2,

I'm working on the next version of coxme, one step of which is converting the bdsmatrix library from Splus to R. Actually, it is a conversion from S4 methods as first described in the Green book to S4 methods as they currently exist. Mostly it's going ok, but not entirely. 1. The biggest issue is lack of documentation. The online help pages have not been a help; they keep saying

Dear all, I'm new on R and this mailing list. We work on spatial rainfall estimation with R and Grass. We have a problem with the krige function from the sgeostat package. We would like to limit the estimated area with a polygon limit. I use a 50 points polygon to describe my work area. The krige function work quiet well without limit. But if I use this option I have the following error

jim holtman (jholtman at gmail.com) wrote: >It sounds like you want to use 'local' to create private variables: Hello, I hope I do not disturb your discussion very much writing in this thread but the topic sounded extremely familiar for me :) My only question is: Is there a good book or more general - any resources that can be used as a reader-friendly introduction to programming

Dear R-Help I am running apply on a data.frame containing factors and numeric columns. It appears to convert are columns into as.character? Does it convert data.frame into matrix? Is this expected? I wish it to recognise numerical columns and round numbers. Can I use another function instead of apply, or should I use a for loop in the case? > summary(xmat) A B

I have a situation where I'm filling out a dataframe from a database. Sometimes the database query doesn't get anything, so I end up trying to place NULL in the dataframe like below. > temp <- NULL > xmat <- as.data.frame(matrix(NA, 2, 3)) > xmat[1, 2:3] <- temp Error in if (m < n * p && (n * p)%%m) stop(gettextf("replacement has %d items, need %d",

As of rev. 61035 in r-devel, setRefClass() now returns a generator function, as setClass() has done since 2.15.0. The convenient style is now: mEdit <- setRefClass("mEdit",......) xx <- mEdit(data = xMat) instead of xx <- mEdit$new(data = xMat) The returned object still has fields and methods accessible as before. See the "Value" and "Reference Class