library(car)
allfails = read.csv("./tp_1/all_fails.csv")
startDate = 1512086401000
endDate = 1514764799000
mtbfSample = subset(allfails, start_session_date > startDate & end_session_time < endDate & (server == 'vsrv10' | server == 'vsrv17'))
leveneTest(mtbfSample$time_between_consecutive_fail_min ~ mtbfFrame$server , mtbfFrame , center = median )