I have looked up the numbers for last season.
The Force had 30 home dates with an average attendance of 3506.
The Bison had 13 home dates with an average attendance of 3305.
Also, Sioux hockey had 20 home dates last year (not counting two exhibitions). I do not know what the average number of home dates for a college hockey team is, but I would guess it is higher then the average number of home dates for a college basketball team. It seems NDSU would be wise to invest in a sport that has higher support in their city as well as more home dates.
Edit: Sources
http://www.gobison.com/ViewArticle.dbml?SPSID=11902&SPID=697&DB_OEM_ID=2400&ATCLID=205030822
http://www.pointstreak.com/stats/pro/attendance.html?leagueid=49&seasonid=5967