The average of allsubgroups becomes the centerline for the lower plotting area. Average of Ranges Example Step 7 - Calculate the upper control limit (UCL) and lower control limit (LCL)for the averages of the subgroups. At this point, your chart will look like aRun Chart. Now, however, the uniqueness of the Control Chart becomes evidentas you calculate the control limits.
Ford Motor Company recommends that the Crown Vic limit its towing to a trailer with a gross vehicle weight of 1500 lbs or less with a tongue weight not to exceed 150 lbs. See HERE.
Subaru's Accessory Hitch is rated for 200 lbs on the tongue and 2700 lbs - 3,000 lbs trailer (strangely they rate the 2.5 for 2,700 lbs and the 3.0 for 3,000 lbs, same hitch though, and probably the same hitch you get -- Which is an interesting question, is it the same hitch?).