I have to test a hypothesis of difference between two means.
I have hospital discharges data. There are 36484846 discharges and mean length of stay is calculated from these number of discharges.
I have also been given the standard errors of the data but the standard errors table mentions that the standard errors of the mean length of stay have been calculated using only 290747 discharges.
I am confused about how will I use such data for hypothesis testing for difference between mean length of stay between two hospitals. Also, which hypothesis test will be most suitable to use?