In statistics, a null hypothesis, often written as formula_1, is a statement assumed to be true unless it can be shown to be incorrect beyond a reasonable doubt. The idea is that the null hypothesis generally assumes that there is nothing new or surprising in the population. The most common null hypothesis is the "no-change" or "no-difference" hypothesis (as in "there is no difference between a sample mean and a population mean"). When testing whether a thing works, and one would start with the null hypothesis that it will not work. The term was first used by Ronald Fisher in his book "The Design of Experiments".