kstones | R Documentation |
Treatment of kidney stones
data(kstones)
A data frame with 8 observations on the following 4 variables.
Counts
the number of subjects in the given classification; a numeric vector
Size
whether the subject has kidney stones
with mean diameter less than 2cm (coded as Small
)
or greater than or equal to 2cm (coded as Large
);
a factor with levels Large
and Small
Method
the treatment method;
a factor with levels A
(open surgery) or
B
(percutaneous nephrolithotomy)
Outcome
the outcome of the stated treatment;
a factor with levels Failure
and Success
The data give the success rates of two methods of treating kidney stones: open surgery methods, and percutaneous nephrolithotomy.
The given data are a subset of that reported by Charig et al. (1986), who also include two other methods of treatment, and also break up the open surgery methods into three sub-groups. The two methods here were chosen because they demonstrate Simpson's paradox.
C. R. Charig, D. R. Webb, S. R. Payne, and J. A. E. Wickham (1986) Comparison of treatment of renal calculi by open surgery, percutaneous nephrolithotomy, and extracorpeal shockwave lithotripsy. British Medical Journal, 292, 29 March, 879–882.
Steven A. Julious and Mark A. Mullee (1994) Confounding and Simpson's paradox. British Medical Journal, 309(1480):1480–1481.
data(kstones) summary(kstones)
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