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.
I used to pull trailers with a LTD, that Crown Vic is about the same ability. However.. The trailers I pulled had a GVW of 2,000 pounds. When you ask Can it pull a TT the answer is almost always YES, however a better question is how much TT can it pull and only FORD can answer that one....