A data set giving the number of publications by doctoral candidates in biochemistry in relation to various predictors, originally from Long (1997).
There is a large number of zero counts. Is there evidence for a separate group of non-publishers?
A data frame with 915 observations on the following 6 variables.
number of articles published in the final three years of PhD studies
dummy variable for gender, coded
1 for female
dummy variable for marital status, coded
1 for married
number of young children, age 5 and under
prestige of the PhD department. The higher the number the more prestigious the program.
number of publications by the mentor in the preceeding three years
In this version of the data set,
phdprestige had been rounded to the nearest integer.
A Stata version with the continuous values was subsequently found at
Long, J. S. (1997). Regression Models for Categorical and Limited Dependent Variables, Sage.
Long, J. S. & Freese, J. (2006). Regression Models for Categorical Dependent Variables Using Stata, 2nd Ed., Stata Press.
data(PhdPubs) # very uninformative hist(PhdPubs$articles, breaks=0:19, col="pink", xlim=c(0,20), xlab="Number of Articles") library(vcd) rootogram(goodfit(PhdPubs$articles), xlab="Number of Articles") # compare with negative binomial rootogram(goodfit(PhdPubs$articles, type="nbinomial"), xlab="Number of Articles", main="Negative binomial")
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