I am working with a database with missing data. I have done "Roderick J. A. Little’s chi-square statistic" and knew that my data are not MCAR. However, I know don't have can I determine if there are MAR or NMAR. I was wondering if there is a test that you may suggest me. Also, how we can know that how many imputations we have to run and what factors determine the number of imputation we should apply.
There is no formal test for MAR vs. NMAR, as far as I know. Point estimates are generally believed to be well estimated in most situations with a small number of imputations, but standard errors and confidence intervals require somewhat more. If computing resources are available to do so, using more is better. Here's a good place to look for advice: https://stefvanbuuren.name/fimd/sec-howmany.html.