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 something works, 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".