The plot shows 'fit' by comparing the expected score based on the model (grey line) with the average scores based on the data (black line with dots) for groups of students with similar estimated ability.
# S3 method for prms
plot(x, item_id = NULL, nbins = 5, ci = 0.95, ...)object produced by fit_enorm
which item to plot, if NULL, one plot for each item is made
number of ability groups
confidence interval for the error bars, between 0 and 1. 0 means no error bars. Default = 0.95 for a 95% confidence interval
further arguments to plot