i've been given 4 data sets, each 30 numbers long. i have to determine whether the data is homogeneous or heterogenous. i've found the median, and marked which are below and above the median. but now i have to determine whether any of the sets are homogeneous and heterogeneous based on the number of runs. i've also been given limits of 12 and 19 as limits for the number of runs. if below 12, heterogeneous, if between, homogeneous. so what is a run? i don't understand how to do this.