Overdispersion is not specific to counting data. In fact, any parametric model including the normal distribution that can't explain the variance in the data set is over-dispersion or under-dispersion.
To address the overdispersion, you may want to re-estimate the model with the new data set. You may also:
- Ignore it because overdispersion isn't a problem if you don't care about the standard errors
- Try NB-P model by William Greene (2008). An extension of NB for dispersion.
