1. A method of removing inaccuracies in curve fits of data representing a physical characteristic of a subject, comprising: identifying a hump or dip in a curve fit of the data; determining a relative error based on a size of the hump or dip; determining if the relative error is equal to or greater than a threshold; modifying the curve fit of the data in response to determining that the relative error is equal to or greater than the threshold; and estimating the physical characteristic of the subject using the modified curve fit of the data.