If I have a set of values(direct measurements of dynamic deformations of a road at 100m) between 3 and~1000, how can I calculate the 2 characteristical values wich limits the interval including 85,95% of all possible measurements on this road? Using stdev and t-Student, the lower value results negative if some values are too high(all values & results MUST be positives).
If the aberant values are the problem how to analyse the dataset to check wich values to reject?