Interpolation When finding percentiles using Figure 2-15, if the locator L is not a whole number, we round it up to the next larger whole number. An alternative to this procedure is to interpolate so that a locator of 23.75 leads to a value that is 0.75 (or 3 4) of the way between the 23rd and 24th values. Use this method of interpolation to find P35 and Q1 for the weights of bears listed in Data Set 9 of Appendix B.