freqbump {equate} | R Documentation |
This function smooths a frequency distribution by adding a small relative frequency to each score while adjusting the probabilities to sum to one (see Kolen & Brennan, 2004, p. 48).
freqbump(x, jmin = 10^-6, Kx = length(x))
x |
vector of either counts (summing to the number of examinees) or probabilities (summing to 1). If x does not sum to one it is assumed to be a vector of counts and it is converted to probabilities
|
jmin |
the frequency to be added to each score point (default is 10^-6) |
Kx |
integer indicating the number of items in the scale (default is length(x) )
|
Returns a vector of adjusted relative frequencies, as probabilities
Anthony Albano tony.d.albano@gmail.com
Kolen, M. J., & Brennan, R. L. (2004) Test Equating, Scaling, and Linking. (2nd ed.), New York: Springer.
set.seed(2005) x <- round(rnorm(1000,100,10)) xscale <- 70:130 xtab <- freqtab(x,xscale) # compare freqbump to freqavg: xbump <- freqbump(xtab[,2]) xavg <- freqavg(xtab) cbind(xtab,bump=round(xbump*sum(xtab[,2]),6),avg=xavg)