Finding the 10th percentile. The numbers are 84, 134, 224, 315, 338,381,428,452,495,519,562,586,609 ,633,653,700,723,767,1108,1250. I just want to know where they got 0.1 from? They have this answer (20+1)*10/100=2.1. 2.1 is not an integer, a 10th percentile is the value 0.1 of the distance between the 2nd and 3rd observations. 134+0.1(224-134)=143. The part that I don't understand is how they got the value 0.1. It is not 10%.