why do we need before and after clustering what is before-after mean when is cluster used what is the difference between clustered and dnd which of the following statements describes a model that has a before- after clustered standard error? why use clustered standard error difference in differences clustered standard errors why does a clustered standard error have to be set before clustered standard error definition what is the standard error in clustered SE why clustered standard errors are important clustered standard error definition can the difference between a prior and a after dnd be used together? how many time periods can you compare a data set in a cluster what are the standard errors in dnd models? which standard error is used by clustered standard errors? clustered standard error definition when does a clustered standard error occur when do you have to use clustering why use standard error clustered model