Hi Dipankar!
Thank you for the new results. Reducing the observed increase in the error rate from 6.7x to 1.5x after standardizing for spelling distance is a significant finding.
For now, I'd prefer to keep the existing generator unchanged and first try to account for this effect in the IEC statistical model.
IEC uses a Bernoulli GLMM that models the probability of correctly processing a word as a function of text length, word position in the response, replacement density, number of rules, and, for target words, the position of the corresponding rule in the list. The model also includes a random effect to account for the individual difficulty of each run.
I'm considering adding a term to this model that captures the effect of spelling similarity. This would apply not only to background words, which should remain unchanged, but also to target words, where similarity between different rule triggers could potentially affect the selection of the correct replacement.
You've already investigated the relationship between spelling similarity and errors in considerable detail, so I'd appreciate your opinion. What mathematical measure of spelling similarity would you recommend for such a term in the model?
Minimum Levenshtein distance seems like an obvious candidate. However, your finding that 28% of misfires involve a rule other than the closest one by spelling suggests that a measure accounting for the full set of distances to rule triggers might be more appropriate.
I'm interested in finding a reasonably simple measure that works for both background and target words, so I can test its effect on the measurement results before making any changes to the generator.